It’s definitely a logical fallacy.

I think strawman kind of fits perfectly.

If you beat me in a fight, you have some bragging rights over me, but if you create a strawman and dress it up to look like me and then BTFO of it, you haven’t beaten me so any bragging to that effect is ill founded.

Essentially if they mischaracterize a person’s position or argument and proceed to attack that mischaracterization, they haven’t actually rebutted the argument or demonstrated the opponent’s position to be untenable.