Such misinformation and intellectual dishonesty - not to mention the startling elements of arrogance - requires correction, regardless of affiliations or your intended audience.
First - as a self-absorbed conceit, I will grant - we must address the notion that Antimagickal professions are inherently antithetical to both the Magickal and Demonic spheres of influence. This is a commonly held belief which holds a faint scrap of truth, but does not touch upon the full depth of the subject. To start, we must first survey those professions that fall within this sphere of influence. Of them, five - Amazon, Outrider, Predator, Ranger, and Wardancer - are inherently physical disciplines and do not channel devotional nor faith-based powers. Unless your implication is that those within the magickal sphere eschew physical discipline as a rule, then they cannot accurately be called inherently opposed, but rather actively opposed - a difference I will elucidate upon briefly.
Past these, we come to the Templar and the Priest. These channel devotional and faith-based powers, and this is where the argument of antitheses oft comes into play. However, it is in a sense a shifting of the blame, and is nonetheless technically incorrect. Magick, as we know, is a fragmented and disconnected form of the Diachaim that the Gods harness and supply to their subjects. The act of fragmentation and seperation changes the characteristics of the flow considerably, and creates a multitude of peculiar resonances with both the pure forms of Diachaim utilized by the Templar and the Priest, and the tainted strains of magick utilized by the Deathknight, Diabolist, and Summoner.
These resonances cause inherent inefficiencies in the channeling of power, and consume small amounts of these respective energies to maintain the reaction. This results in the effect often seen by those who carelessly forget to discard magickal artifacts when they change their affiliation, draining attunement, devotion, essence, and so on. These resonances are often harnessed for intentionally destructive use as well, seen in the imbibing of totems and runes, the Rite of Banishment, and other related disciplines.
Again, however, these all come back to the idea of active opposition. The ideal of mastery of the self and purity - to differing extents, of course - is held sacred not only by the Avengers, nor only by the Illuminai, but by the vast majority of those who place themselves within the Antimagickal sphere of influence. Whether they oppose due to past and present experiences, religious belief, zealotry, or simply because they believe it is the right thing to do, the important fact is that they choose to oppose.
Yes, being around pervasive fields of magick tends to have negative effects on even those adhering to purely physical disciplines, but this is primarily due to a lack of training or natural talent. I will note that the fact this training tends to be the first thing forgotten upon a change of affiliation suggests subtle physical and mental changes wrought in the wake of repetition, but such a hypothesis would require extended study.
This does not touch upon the Monk - I admit that while I have been personally trained in the arts of Telepathy and Kaido, their inner workings still remain rather obscure to me. However, I have no reason to believe yet that they are anything other than a particularly strong expression of innate mortal talent, as outrageous as it may seem at first glance.
I will also note that Alesud currently possesses the knowledge of the Outrider - presently distinguished from the Hunter only on the grounds that she does not utilize the ether-based skills. Even if you choose to reject scientific explanations, this fact alone questions the concept of the Outrider being 'inherently antithetical' - unless you believe that the ability to ride a horse and shoot a bow at the same time grants one the power to oppose all that magick stands for.
Second, we come to the humorous notion of cities and councils governing the actions of the Divine. If you have not noticed, historically, faith has a way of transcending boundaries such as politics and walls. If you outlaw Her, She will find a way back into the hearts and minds of your subjects, and they will not be willing to forgive you easily - assuming they do not manage to overthrow you and carry your head about on a pike first. If it does not openly affect you - and I daresay that an Outrider being amongst the followers of the Lady of the Night alone is hardly the concern of Kinsarmar, not that matters of jurisdiction have ever prevented the City of the North from overreaching - then you are best to let it be. Blocking her from your walls is one thing, but wide-scale persecution is quite another. You cannot afford the fallout, though I surmise that you have already allowed Galt to dig you a grave of substantial depth.
Third, the notion of purity of magick. This is itself a questionable thing, as well - magick in its true and purest form is Diachaim, which can be manipulated with similar methods and many more besides. However, there is a grade of purity while still being within the confines of the lesser power - the refinement processes required are rather impractical, however, rendering it hardly efficient for daily use. Short of falling to the basest forms intertwined with Demonic energy, all magick falls within what should serve as a sufficient band of purity for use.
Ideologically, of course, the notion of purity of magick runs far deeper and in far more directions. It is most often used as an excuse to marginalize those the espouser dislikes and to wreak havoc upon one's political enemies. I am familiar with this, too, as I once used such tenets to great effect. However, I have discovered that it is at the core an excuse - one used to justify the use of fragmented and debased forms of power as a quick route to disappointingly temporal power, in the absence of a long and arduous journey to self-transcendence. I do not judge you particularly harshly for your choice - it is one full of temptations and lures, and temporal power can be quite satisfying for a time - but I do suggest that you consider what you aspire to, and act accordingly.
In closing, if you truly wish to present a united front, then you are best off uniting. I suggest clamping down on those who are truly fractious, and I surmise that these are not the same people that those shouting the loudest would have you believe they are.
Or, you may continue to consume each other until you have crumpled to dust and ash yet again. It would be quite dull of a course to take, but it would give me free reign to focus exclusively on my most sincere enemies, and that is in itself quite appealing.
-- SV
Penned by my hand on the 23rd of Artificium, in the year 672 AD.