Isn't it a red herring? Maybe ad hominem?
A straw man would be changing his argument so they can argue against something they never argued.
A red herring is meant to distract. He is trying throw you off talking about his math by mentioning he's anti-vaxx.
As hominem is a personal attack used to dismiss the argument.
Guys, if you stop responding to trolls like random boy, they will go away. Stop feeding them.
To expand on this further for the benefit of DarthOne and others that are less in the know about this stuff, here are a couple of illustrative examples:
Person A: I believe illegal immigration is not beneficial to our country and should be dealt with.
Potential responses:
1)
Person B: Really? Well, here are 10 reasons why white supremacy is terrible.
That was a strawman. It's a bad argument because person A never said anything about white supremacy. Person B just assumed that person A wants illegal immigration gone because he's a white supremacist, so he attacked him on that point - that he never made. There could be a million reasons for curtailing illegal immigration that even have nothing to do with race at all.
2)
Person B: Really, Person A? Aren't you an anti-vaxxer? Clearly you're an idiot, so why should we listen to your opinion on anything?
That was an ad hominem attack. Person B didn't refute person A's point, rather, he attacked his character directly. Regardless of any other correct or incorrect opinions person A has, his argument should stand on its own merit. Other arguments made on other topics at other times do not influence any argument made in the present. Even if person A is genuinely stupid, a broken clock is right twice a day, and calling his character into question is not evidence of anything.
3)
Person B: Well, the immigration certainly benefits the lives of those immigrants, so we should let them in.
That was a red herring. It's a bad argument because it has nothing to do with person A's argument, that illegal immigration is not beneficial
to the country. It goes on an unrelated tangent entirely, maybe even one that can genuinely be examined later, but that did not do anything to refute person A's point. Even if immigrants do benefit from the immigration, their arrival could still be bad for the country. It's an argument that distracts from person A's point in the hope that he forgets about it, rather than refute it directly.
Hope that helps.