To many at the more "evangelical" end of organised religion, and especially within Christianity, their faith isn't a private thing, because the tenets of their faith require them not only to live according to the dictates of that faith, but to testify, evangelise and convert. Activities which are very much not a "private thing", and which in effect politicise that faith.
Add to that the fact that the hierarchies of most organised religions within the UK attempt to exert influence over social policy in the UK in an organised manner, which atheists don't subscribe to, and you (yet again) don't appear to actually have much of a clue about the subject you're holding forth on.