When the best you can do is attack the person who shared the material, you know you’ve lost.
Sorry Mr. Reacher, that's a recognizable debate tactic, but the conclusion doesn't necessarily follow.
If someone responds to evidence by attacking the person who presented it instead of addressing the evidence itself, that's an ad hominem argument. It doesn't establish whether the material is true or false.
But criticizing the source isn't automatically an ad hominem fallacy. The source's credibility, incentives, methodology, context, and whether the material was authenticated can all be relevant to determining whether the evidence is reliable.
A stronger principle would be: If you want to refute a claim, address the evidence and reasoning behind it—not merely the character of the person presenting it.