I've been on both sides of this argument.
As a psyker in a game that's gone from first level up to Ascension, it is wearing that my companions still have prejudices about my witchiness, but (as Darth Smeg observes) are more than happy for me to patch them up, remove their fatigue and make enemies conveniently fall asleep. Fortunately, I've never had a world-shatteringly awful Peril (having been more than hesitant to use my abilities for many years).
I did once spawn a pink horror, but we were in an apartment block and it materialised outside the window, plummeted several floors into a crowded market and set about devouring people. Sure, there was some interparty tension (mainly the Scum trying to prevent me from going to help, insisting it was outside the remit of our mission...) but we got through it.
The makeup of your group and the relationships people have with the Psyker will play a huge role. In the game I just mentioned, the Psyker had long been the voice of sense and moderation, and the others respected his position in the group, and were thus prepared to overlook phenomena they actually had little knowledge of.
From the other side, I played a fanatical Cleric. After a lot of tension with the group's Psyker, he unwittingly unleashed daemons on us that gave my Cleric 9 Corruption in one go. Unsurprisingly, he turned around and cut the Psyker in half with his Greatsword. The Psyker's player was pretty philosophical about it.
Maybe, if you think it's going to be an issue, you could have a talk with your group OOC (especially the Psyker) and make a decision to ensure no hurt feelings or misunderstandings further down the line.
In our game, the gutted Psyker burned a fate point to stay alive (the Cleric was soon too busy with a mutant abomination to check his handiwork) and later got a fresh one from the GM for reasonable in-character reasons. No harm no foul, and it led to cool roleplay.
To conclude my waffle, you establish your character and their values, and it's your call how they would react. You should never feel like you're forcing them to act (or not act) for OOC reasons. At the same time, maybe you could take a moment to balance all the times your Psyker has saved your hide when considering whether or not their loss of control should be punishable by execution.