What is the problem with him having a coworker who is single?
Maybe this is only something that happens in my country/culture, but sometimes people say things like “everyone is x or does y in work” and they don’t literally mean every single person, they just mean that it applies to almost every one/the majority of the people in the situation. I don’t think it means they’re intentionally hiding something or being misleading, it’s just a colloquial phrase/wording. Hyperbole I guess too. So personally I wouldn’t have taken his comment as a literal, solid fact.
Also workplaces change and co workers move around, things change.
Can you explain why this has upset you? Understanding why you feel what you feel is important in my opinion.
It seems this isn’t the first time you’ve felt like this or had a strong reaction to this type of situation, judging by his reaction.
Is there a reason why you can’t just talk to him about it?