For the record, I have a teaching certificate, and one of my subjects at college was music. I taught music in schools for twelve years, and continued teaching privately until about a year ago.I have been the organist at my local church for over thirty years, and we used to have a children's choir of around twenty singers until about eight years ago. The choir, in my opinion, was 'eroded away' by the introduction of the Saturday evening 'Vigil Mass', which resulted in families 'fulfilling their Sabbath obligation' on Saturday evening, rather than Sunday morning.
Church choirs are often organised by untrained volunteers, and it is not unreasonable for them to ask for help.
As for choristers being trained to sing in tune together versus those being told they cannot sing - you'd be surprised at how touchy people can be! Singling someone out, either as a good or bad example, can easily be misconstrued, and a skilled teacher learns to recognise (and minimise) the risk.
Mudcat is probably the first reference for many musicians who are not trained teachers, and are counting on the experience of others - not only for advice, but where else to look for advice.
I can give practical advice, but am not aware of websites which are available simply because I was not 'connected' when I was actively involved.
If, indeed, this thread is a 'flame', it doesn't matter - who really cares?! It has provoked comment, and has provided information that may well otherwise not have been posted.