One quibble: it ain't new. I've been accused of being a bot on /r/conspiracy for well over a decade.
But my response has long since been the same: does it matter? Whether I'm a bot has absolutely zero bearing on the truth of what I'm saying. Don't get me wrong, we should definitely do something to curb botting, but I agree with you: if you find yourself using it as a reason to dismiss an argument you're just relying on a garbage ad hominem.
Im way too sexy to be a robot.