I always thought it was polite to call him “President Bush” when talking about him in a formal situation. Of course, I just call him “Bush” when talking about him in a general sense, like discussing policy.
I thought it was rude when Michael Moore said, “We are against this war, Mr. Bush.” He should have said, “President Bush” or “Mr. Bush”.
I also thought it was rude when President Clinton called President Bush, Sr. “Mr. Bush” during their debate, when Bush was still President.
No, I’m not a right-wing loony. Those are just the first two instances that came to mind.