Do they always refer to you as a profligate and treat you like crap when you talk to them? even if you help Caesar and have the highest reputation with them?

Nah. I tend to get responses of just "Ave." or "True to Caesar." when my Legion girl talks to them. Once I got "We each serve the Legion in our way". Never once have they called her a profligate.

What's so great about NV is that the people address you based on your reputation.

-Nukeknockout

the legion are sweet... good to know ty

"Hold yer tongue wastrel !"

Their dialogue for when you are idolized with them is actually quite awesome.

Boosted rep with them makes them treat you like their own
Ave, True to Caesar! Vale!

There is a certain Centurion who will always refer to you as profligate, even if you're idolized by the Legion...

But that's just one exception, otherwise it's like Gingy said, the comments made by passing Legionaries are quite awesome when you're idolized by the Legion.

"Ave, Amicus."