I like playing my music loud in the car too, but I wouldn't have had to be asked to turn it down. If I have my window down for any reason in town, at a stop light, parking lot, whatever...I will turn it down so others don't have to be subjected to my music. After all, they might not like the same type of music I like so why should they have to put up with hearing it?
I absolutely hate it when I'm at a gas station, outside pumping my gas and some idiot pulls in and leaves their "music" turned full blast with the window down while they're pumping their gas. No concern for anyone near them who might think their "music" is garbage.
Have your music as loud as you want while driving. When parked with other people in the vicinity show some courtesy and turn it down.