This is a reasonable concern.
I will note anecdotally not all role players are playing with a full deck -- though I am more familiar with role playing gamers, not LARPers (granted: not entirely separate groups). Some are mildly cracked, sometimes harmlessly -- the guy who exclusively played female characters and might have identified as trans had he been born later -- and some not so harmlessly -- the gal who forged her own sword which she took with her everywhere, even the mall, by concealing it under a cape, and genuinely believed she was the last special warrior of some sort from a fictional series.* She believed she was female to signify she was the last.
So that may complicate sorting out who is just playing games from who is a genuine threat of planned violence.