This is a popular statement in American English now.

For fun, I searched Google for “You have an attitude.” (with the quotation marks, to avoid variations) and got about 46,200 matches.

But this statement means nothing except for the negative connotation beneath its euphemistic form.

Someone usually says “You have an attitude.” to tell the listener that he or she has a bad or negative attitude.

But the noun “attitude” by itself has no positive or negative value.

Can you imagine someone, such as a non-native-English speaker, first reading or hearing “You have an attitude.”?

The statement would be meaningless to such a person.

The noun “attitude” must be modified by an adjective to give it value.

Otherwise, you are speaking in euphemisms.