Instead of trying to contain most Weird Shit they encounter, Legion mostly just tries to destroy it, or first contain and then later destroy.
This is as a matter of both hate and practicality, there's only so much room at the derelict hospital they've taken over to contain dangerous substances.
It also means magic people doing stuff that messes with Mere Mortals don't get the kid gloves treatment. Diplomacy is only considered for people just screwing around or otherwise not making themselves out to be a major threat.
some people didn't have time to cast a "stupid ass ward spell or whatever the fuck" (t. Director Arigah) before a rifle blast from Alpha took off the upper half of their torso (and damaged the barrel of the prototype rifle it was using)