This is an ad hominem attack on a persons character; it is a tactic used in, typically, internet argument conversations by trolls who have no real criticisms to make. Used most often at a certain point in the conversation when they know that they have lost the argument, & perhaps they started without a real argument in the first place, the troll uses projectionism to defend themselves.
2. Projectionism is particularly common among racists & other bigots. They will commonly make bigoted comments & then deny that they are bigots; and further defend themselves by accusing the person that normally initially accuses them first of being the very thing that they more often than not end up accusing the other person of being.
Tho, it is possible, & certainly not unheard of, for a troll to use projectionism against someone before that someone has a chance to say ...ANYTHING... to the troll, as trolls are known to attack anyone unprovoked. Regardless of the details of how the troll and their victim(s) begin the conversation, in using this particular troll-tactic, a troll never backs up their comments or accusations with facts, only unfounded criticisms, and often outright lies; which is at the heart of an ad hominem personal attack.