It means people who do not follow the actual teachings of Jesus, but use the Jesus brand to claim legitimacy for their ideology.
What does that mean?
Only 13 per cent of Americans support abortions in the third trimester.
Are 87 per cent of Americans, therefore, " fake christians"?
If you support cuts to the safety net to reduce your tax bill you could be a fake Christian.
If you’d rather lock up than accept asylum seekers you could be a fake Christian.
If you’d rather roll back environmental protections than accept the demise of coal and then oil you could be a fake Christian.
If you are willing to fight for the unborn more than the living you are likely a fake Christian.
If you still support Cheeto Jesus you are a fake Christian.