so what? they all do that!

I can't identify a fallacy, because I can't identify an argument.

Is the hypothetical person saying, "it's okay for Trump to lie because all politicians lie?" That would be a non sequitur as a lie is immoral regardless of who tells it or how many people tell - therefore, even if 'all politicians lie', it would not be right for Trump to knowingly mislead people with his own statements.

they never go so far as to say its ok for him to lie, its more like a "it is what it is" and "hes not the only one" kind of scenario

"It is what it is" would just be a thought-terminating cliché.

"He's not the only one" is a red herring - in a discussion on X's negative behaviour, pointing to Y's failures - or alleged failures - is misdirection in debate.