I like to sing popular folk songs with a strong chorus line that the audience/joe public can recognise and join in with with all their hearts.

No song should ever be banned/dismissed/mocked or degraded because of it's popularity and some sense that it has been 'over-sung'.
It shouldn't matter either whether it is sung well or not so well so long as 'the audience' on that occasion gets the gist of it and joins in and enjoys it.
It all depends on the company you are in and the general ambience at the time. It doesn't take long to get a sense of what will go down well and what may not go down well.
So to hell with 'Songs you shouldn't sing' - sing them all I say and have a jolly good time.
Some sessions just get far too stuffy and up their own do da's and in my experience, only work for the self-centered and self-obsessed 'inner circle' and don't work for those listening in and hoping for a song they can join in with.

This reminds me of the time way back in the 1970's when me and my wife to be went to see a Ralph MacTell concert in London and he refused to sing "Streets of London" on the grounds that it was over-sung and he was growing bored of it - guess what? - about a quarter of the audience (including us)were brave enough and incensed enough to walk out in disgust.
How ignorant is that!? Especially when that one song was his pension for life!
Since then I don't believe that there is any song you shouldn't sing in a UK folk club.