I have an in-law family member who hero worships Charlie Kirk. He wears the T-shirt and has a Charlie Kirk sticker

[Doodley]

on the back of his car. What would you think of him, based on this, and how would you handle this situation?

[mahatmakanejeeves]

1. Civilly.

Age? Occupation? Education level? "In-law" meaning what?

Don't bring up the subject. If he does, you don't have to agree with him. You also don't have to get in a shouting match with him.

Before giving a response, ask yourself, "Is this how I want to be remembered?"

And good afternoon.

[underpants]

2. I'd just avoid the conversation if possible

You already know enough about them to know you don’t need to hear their view or opinion….mostly because it’s probably not really their own.

[dem4decades]

3. I'd just avoid him. I'd avoid him if he was a family member

Never mind an in law

[Ocelot II]

4. By ignoring it as much as possible. There's no point in getting into it with those people.

[RockRaven]

5. I would think they are a likely irredeemable shitbag, and

I would handle it by not wasting my time interacting with them when avoidable -- the payoff for being wrong on that knee-jerk assessment is not worth the headache that would come with being correct.

That is, as you note, solely based on that one fact you have shared, however, and in a non-hypothetical situation surely more than that one isolated fact would be known so this answer is necessarily of little real world usefulness.

[Norrrm]

6. Good advice so far.

[Dan]

7. I would not allow his influence around my children.

[Melon]

8. People believe different things

They are opinions. Does he tell you what to believe?

[ForgedCrank]

9. You handle

it by keeping politics to yourself and do nothing as long as he isn't harassing you about Charlie Kirk all day. If he does, kindly let him know that you'd prefer to not talk politics or religion for the sake of civility. If he still refuses, simply stay away form him because lashing back is the same thing, don't be like that.
You won't be changing his mind and if he's treating you decent, you do the same because that's what decent people do.
As far as what I would think of him? It wouldn't matter to me because I recognize the right of others to have differing opinions and I don't hate them for it. I may secretly think they are wrong on some things, but that is irrelevant to them and not worthy of a family argument.
Anyway, that's my advice.

[sakabatou]

10. Avoid talking about Charlie

[The Wizard]

11. Bigotry is a negative character trait.