Action verbs used with "keep" sound normal, like "keep doing," "keep smiling," etc., but "being" sounds weird with it.
For example, this:
I won't talk to you if you keep being rude.
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Semantically, "to be rude" is an action, not a state. "Be" is of course a stative verb in this construction, but the phrase as a whole implies a specific rude action rather than a general state of being. You can say "keep being rude" just as easily as you can say "keep acting rude," and they both mean the same thing. However, it might sound odder if you said "keep being tall," because "being tall" is not semantically equivalent to an action, so it's unclear what that phrase would mean. "Keep being tall" is not wholly ungrammatical, but it is unidiomatic.