Hazarding a guess that they feel OP is using schizo as a shorthand reference for crazy/delusional, given the context is Internet conspiracy theories. They possibly feel that it is being used as a perjorative which disrespects folks who struggle with schizophrenia. In essence, calling something you find crazy “schizo” is the same as calling something you find dumb “retarded”.

I don’t have a dog in the fight one way or the other, but, in the absence of their reply, that’s my assumption.