Would it be correct to say that whatever circumstances existed where the person was suicidal to such an extent that you _knew_ they were suicidal... were _not_ responsible for the suicide? I mean, doesn't the definition of "suicidal" imply that suicide is a distinct possibility even if no one takes further negative steps?
Or perhaps to put it another way... would this ridiculously shitty conduct be any less so if Aaron were alive today?
Seriously, the notion that things like suicide are controlled by _anyone_ is pretty ridiculous. Sure, sometimes people can make a conscious choice that changes outcomes, and there are no doubt things one can do that improve or reduce the odds... but definitively laying culpability on someone's shoulders is rarely possible.
I think it is enough to say that doing shitty things to people who really don't deserve it is bad, and it is worse when you know those people are already fragile and/or suffering. Engaging in histrionics and scapegoating, if anything undermines the argument.
By itself? No. Merely knowing is not sufficient to make you responsible in some way.
However merely knowing is not what they are accused of.