The term "cowboy" as it was used can generate a visceral response. It is often used as a pejorative by Americans living on the coastlines to disparage people in the heartland of the US.
To complicate matters, the WAY it's used makes all the difference. IF it's used as a synonym for toughness and a "take the bulls by the horns" attitude, it's not insulting. If it's used as a synonym for unsophisticated, uncouth, wild, undisciplined, ignorant, or unintelligent, it's an insult.
When used by non-Americans in the insulting form, it's perceived doubly-so. Wesley's reaction is not atypical, nor is it particularly overblown, though it is a strong reaction.
While I'm loathe to language police, I would caution people against using the term as a synonym for lack of tact, sophistication, skill, or intelligence as you WILL offend people.
This is not policy, and I am not a moderator, but I think we could benefit from a little more civility here.