No. Some politicians are corrupt ; certainly. A lot more aren't corrupt, but come from powerful moneyed groups (it's not corruption ; it's where the opinions they trust come from). But it's precisely the notion that ALL politicians are corrupt that shield and protect the actual corrupt ones. Because when we see corruption, far too many voters go "Eh, they all do it anyway, and we know this one" ; or "No one's gonna be better", or worse they just refuse to vote, abdicating their power to actually punish politicians and try to improve things.
In short, while there is some basis to the sentiment, it's the worst possible sentiment to hold in regard to the situation.