Use a long spoon!

"He who eats with the devil should sup with a long spoon" as the old saying has it.
Sometimes Christians have to deal with secular organisations - that is clearly ok. But there is a fine line to be drawn as to when Christians should withdraw, particularly from political groupings, if that organisation is institutionally opposed to Christianity.
The term 'social justice' once had a meaning which resonated with Christians. Today it means any leftie agenda whatsoever. The left today despise Christianity. Shame on those who try to keep a foot in both camps.
Consider moral issues then ask how any Christians can ever allow themselves to vote for Labour, Green or Lib Dems any longer, let alone be party members. The argument of 'making changes from within' only works to the most limited of extents and yes, I am aware that the Tories are pretty dreadful too.