Ever heard of someone saying "fuck cars" in person? Where the conversation just stood on "fuck cars", and stopped there? When someone on the internet says "fuck cars", it's because he's expecting to get some dopamine from getting liked by similarly minded friends who also hate cars.
If his purpose was to have a discussion, to convince you, it wouldn't be "fuck cars", it would be "cars are polluting". And even if he's an arrogant asshole in real life, you could explain how cars are useful to you, and ask what he's suggesting to do. Maybe 1% are such total careless assholes you shouldn't be talking to them, but others will try to come up with an answer, and if they fail to give it, they will remember it.
If his purpose was to have a discussion, to convince you, it wouldn't be "fuck cars", it would be "cars are polluting". And even if he's an arrogant asshole in real life, you could explain how cars are useful to you, and ask what he's suggesting to do. Maybe 1% are such total careless assholes you shouldn't be talking to them, but others will try to come up with an answer, and if they fail to give it, they will remember it.