Is generalizing about any identifiable group always wrong?

When is it not wrong?

For example, I could say something like, "Communists want to overthrow our financial and social and governmental systems. Its a system under which my ancestors and I have thrived and I believe my children will thrive. This is a threat to my way of life. Therefore, all communists threaten my life and the lives of my children."

Substitute any ethnicity or nationality or religion. Notice how the degree of offensiveness changes depending on whom we put in the dock.

Botnst