As a group? None in particular.
As an individual, as Hermetics can still sometimes draw the attention (and blessing) of an ideal, a way of life, a supernatural entity that may be the embodiment of some human ideal? I dunno. Pick one. It'd have to be a non-douchebag Mentor, that wouldn't inspire whole tons of douchebaggy behavior on the part of the mage in question -- Adversary doesn't last long in a military environment, for instance, and you've got to be good enough at your job to justify the headache, if you take one of the "goes berserk" Mentors -- but in my opinion most Mentor Spirits would be fine.
Or, rather...most trained hermetics would be valuable enough that turning someone away for having a Mentor Spirit would be not-fine. So long as it doesn't make it so you can't do your friggin' job, the Tir should be accepting of someone who gets a little boost here and there from an obliging Mentor. So long as overall you're still a competent, reasonable, rational enough spellslinger -- not one of those hippy bullcrap Shamen with their weird rituals and special rules and stuff -- the Tir should be fine with you.