Ignore, ignore, ignore. Publish their private e-mails so that everyone can see just what kind of "Christians" they are, but don't engage them in conversation.
I almost lost the faith in 1991 because of the lies and distortions of these kinds of blockheads.
I recently lost my kid sister to these kinds of blockheads, and my younger brother too several years ago.
They were never taught Roman Catholicism, but instead were fed the spirit of Vatican II crap instead. They were easy prey to deceivers and liars.
A prophet is never accepted in his home. I'm not a prophet, but neither have I been able to replace the crap my siblings have been taught by these kinds of blockheads with the beauty of Truth.
For me and many others, this is personal. I don't want others to fall to the lies I almost fell to, and my siblings have indeed fallen to.
This is spiritual warfare, and the stakes are high. Eternal Savation is at stake for some of these folks.
Don't feed the bears?