A vulgar person uses words that are in poor taste, they are obscene, offensive, uncouth and coarse. A person who is coarse is not refined, not delicate, has no manners, and may be lacking in social graces and does not have good etiquette.

Vulgar and coarse are synonyms. Both mean crude, rough and rude. If a person uses four letter swear words all the time, you would describe that person as vulgar or one who uses coarse language.You are right, it certainly creates a negative impression.

Good question! Vulgar is stronger. I'll give you some examples, but obviously because of the topic they will be potentially offensive. Because of the content of the examples, I will message them to you: I don't want to upset people in here. :)