I hear this argument a lot and it is what I think is called a strawman argument. I doubt there is an adult on the planet who doesn't lie. But the point is what is the effect of the lie.
If a politician convinces you to vote for something to your detriment by lying, then that is bad, for you.
If a politician causes a positive outcome for you by lying then you won't mind.
In my view the British electorate have been convinced to vote for right-wing policies benefitting a small number of elites, by being lied to. Hence bad.
Just my view. I'd happily vote for a politician who swore they would never introduce a wealth tax then did it on the first day in power