Toxic masculinity isn't a word meant to diminish the very idea of masculinity, it's meant to describe the forms of it that hurt other people and men. E.g. "tough love" parenting hurts the son and robs the father in the future of a healthy and loving relationship with their son.

Toxic feminity is a concept but you correctly pointed out that it's tied to patriarchal ideology, it basically is a form of feminity that tries to validate patriarchy. The reason it isn't focused on misandry the way toxic masculinity is focused on misogyny, is because in western society, men and the culture of men had the vast majority of power. It's kinda similar to how one can certainly be prejudiced against white people in the west, but you'd have a hard time arguing for the existence of racism against white people in the west, since that word more describes prejudice with the weight of systems behind it. Thus the "n word" is "the n word" while saying "cracker" is generally fine or at least not nearly as socially unacceptable. Does that frustrate you as well? If so, it could be a good starting point for you to learn why your idea that we shouldn't be allowed to criticize "one side but not the other" is a bit wrong headed.

Anyway, so too does toxic masculinity and patriarchy describe something much larger than one man or one family.

If we hesitate to use these words because we're afraid of not being "both sides" enough or "fair," we're robbing ourselves of the opportunity to treat the root cause of, as you say, some antisocial behaviors. E.g. the incel movement is male-driven, the incels who got radicalized and driven to violence were all men, and incel culture latches on to the most toxic aspects of western male culture and uses it as their core ideology. If we want to analyze and perhaps "do something" about the incel movement, we have to be honest with ourselves about it and the history that led to it.

There is no feminine equivalent of this. There's incels that are women, but there's no massive internet movement that touches all aspects of culture and sometimes leads to school shootings. It's an issue of toxic masculinity, among other things, and feminine culture simply doesn't come into the picture. Shall we not talk about it until some more women have done school shootings for misandrist reasons?

That isn't inherently misandrist. You can talk about this without lumping all men into it, the same you can talk about the grave American crime of chattel slavery whole also including the abolitionists who sometimes put their lives on the line to resist it.