If he's a British man in the UK then I would struggle with it. I wouldn't leave an otherwise happy, loving, secure marriage over it but I would have big questions and be very upset.
But if in the USA then I just don't know. Instinctively, yes, I wouldn't like it but I also think that there must be something that we just don't understand in the UK that has allowed Trump back into power. I know several Americans who I like very much, respect and consider to be good people who all voted for Trump. It's incomprehensible to a British mind but it has made sense to dozens of millions of American people who are not that different to us. They cannot all be wrong/stupid/misguided/bigoted/bad people.
I have only engaged with two people over it directly. They both despise Trump as a person. But still voted for him. Both cited cost of living, taxes and the belief that they will be better off financially as a family. Direct quotes from one: 'I don't need Trump to be my friend (ugh), I need him to fix this country.' and 'He's a bad person for sure, but I think he will be good for America.'
You could say those are selfish, deplorable reasons for voting Trump. And I'd agree they possibly are. But I also think they're understandable. Most people, when it comes to it, will probably vote in their own self interest when it comes to it - or at least seriously consider it. And there is no even slightly credible 3rd option in the US for them to take as an alternative or protest vote. As a silly, much lesser, example: I couldn't bring myself to vote Labour because I teach in an independent school and felt I would voting myself out of my job. Even though I believed they would be better for the majority of people. But I could never vote Tory either. So I voted Lib Dem (I've actually always been a Lib Dem but would have voted Labour to help get Tories out if it wasn't for their private school policy - pure self interest). I know Lib Dems aren't a realistic 3rd option but they've got a lot of MPs. Not something that can happen for any 3rd party in the US.
So, no, I would disagree with someone who voted for Trump but I can understand their reasons and it wouldn't be a deal breaker. If they thought Trump was a great person on the other hand ... yikes!