I've played enough WH40 RPGs to come to the terrible realization that humanity's paranoia over psykers is absolutely justified.
A Psyker is like a walking, talking demo-charge that could blow up at any moment and for any reason. I vividly remember one game in which a psyker tried to heal a wounded guy in a park (simple minor power). He rolled Perils of the Warp and killed himself, the patient, the Arbitrators who were guarding the park's entrance and severely injured the rest of the party.
Oh, I can certainly accept most of the Imperium's anti-psyker sentiments; every psyker is like a little, walking door, and when the doorbell rings, it's always Chaos Pizza Delivery, and a pie topped with Sardines of Tzeentch. Of course, I also believe that some of it is simply Humanity's complete inability to work together, in some ways, and their abysmal notetaking abilities, seeing as they've lost more stuff, and the info on how to use it, than I can even come up with a good pun for, here. If they were willing, and able, to look at it more from a neutral, or scientific standpoint, I believe they could approach the Eldar's control, and I rarely ever hear about an Eldar tapping into the Warp, and blowing up a Craftworld park. They spend so much time fearing and reviling it, it's no wonder they have come so short on anything approaching making psykers safe. Overall, I can appreciate that, of course, since it fits in well with the grimdark angle the game likes (it still sort of amazes me the gov't doesn't just keep the Emperor's vast psychic powers a secret, since they are to be feared).
I often laugh at the weirdness, though, as they hate psykers, but they hate blanks just as much. When I get the book (OW), I'll have to see if the Gland Warrior and Untouchable templates can easily integrate in.
And, if I am feeling silly/anti-canon, I can keep working on my story, wherein a Human psyker/Guardsman deserter (Alistair, but I am considering changing the name) has been prophesied in an Eldar reading to be VERY important. To that end, he has been "taken" to one of the Craftworlds, under the escort of the main heroine, Farseer Astrina, against the wishes of most of the other Eldar, where she plans to "stabilize" his mind, and strengthen him against the rigors of the Warp (effectively, train him in the Eldar way, and garb him in their stuff). Right now, where I am writing, her sister, Ynella, a rather naive, sweet Bonsinger, is using her own gifts to try and forge a set of rune armor, and a played down ghosthelm for him, but attuned to his unique aura signature. It's proving to be a fun story to write, with Guardsmen, Inquisition, Eldar, romance, and crap. About as "not quite in setting" as I can get.