Fallacy

Stating that something existed in a lesser form before something else makes it worse does not invalidate the argument that something made it worse.

There's probably a named debate fallacy for this.  What's the name for, "You're wrong because of a reason that doesn't actually prove you wrong"?

Example from a deleted comment (paraphrased):

Because the mafia existed before prohibition, prohibition did not make them larger and more powerful.

Because some euphoric drugs were illegal before prohibition or the war on drugs, the small gangs did not grow into large cartels.

Making drunk driving illegal changed people's behavior, therefore prohibition must have been effective.

These three "arguments" were contained in a multi-paragraph meander that didn't actually refute what I had posted, but did manage to tangent but hard.

What do the rules say about going off on a tangent?