I'm going to play my music fairly loudly in my car
I don't quite understand, why would you play music in your car loudly?
Because it makes me feel cool.
Even though you might enjoy the music and feel like people think you are cool because of it, usually people do not think that. Usually, people are annoyed when others play loud music in public. Consider keeping your music at a reasonable volume in public.
I could give a shit what people think. I'm in my car so I'm going to play my music loud. That's the law.
I have to disagree, disrupting people with loud music is actually against the law and if you continue doing it, you might be reported and will face consequences with the authorities so I suggest you stop.