Slam dunk for his case in my opinion!
No, he was behaving inappropriately as the guest of a client, embarrassing the client and his employer. Content of his speech isn't the issue.
"He wasn't drunk, he was using his First Amendment rights!"
What does the first ammendment have to do with it?
Can you quote the part of the First Amendment that says your speech is guaranteed to have no negative consequences, and the part that nullifies your employer's rights of free association?
First Ammendment rights have nothing to do with the actions of a private entity, the business.
You also do not have an absolute right to make any noise you desire to make, even at political events. You have the right to say what you want, but not always everywhere you wanna say what you want.
"If I hear the words "free speech", I'm going to hurl..."
hurl.
His First Amendment rights mean the government can't stop him. Is he in jail for criticizing the president? The First Amendment doesn't protect against (perfectly foreseeable) consequences; it doesn't repeal cause and effect.
There is no first amendment rights enforceable against a private company.
First Ammendment protects you from the government, not your employer.
Welcome to the real world.