justify their religion?

Hmmm. You seem to think religion needs to be justified?

What about opinions, do they need to be justified as well?

And what happens if their justifications (for both cases) does not please you, or does not meet your criteria? Serious question.

Why be religious if you aren’t going to go all in?

Yes, that is a weird and sad phenomenon. Lots of people seem to just not care anymore what they even think or believe.