The number of people who drank the kool-aid is astonishing. To the same tune, I think that if you tell people that politicians lie, majority of them will be deeply shocked, hurt, and offended.
Could be a generational or cultural thing, though.
In the US a huge portion of the population doesn't vote, I would expect those that think every politician is a crook.
The other side that does vote thinks the other politician lies and their politician is the good one.
If you do it as a blanket statement — i.e. all politicians lie all the time — then yes, I will be pretty irritated.
Some politicians spout dangerous nonsense most of the time.
Other politicians can be trusted most of the time, and when they lie it tends towards 'spin' or 'being economical with the truth' (such as: "we are spending more on education than ever before" — when this is true in nominal/absolute terms but false in real/per-pupil terms).
There is a world of difference between these positions, and treating them alike (as many do) undermines democracies.