Agree with parts of what somebody is saying, then say however this (make your point).

It might work with someone who's reasonable and not firmly wedded to their position. A lot of people aren't like that, though.

If you can hide your intentions, or know how to word what you want to say well and show that you are genuine in your desire to have an open discussion, possibly.
Otherwise it can come across as you trying to get them to shut up so you can say your piece, or something else of that nature.

I think it's better if you agreed completely..there's a reason why shrinks are mostly listening and nodding their heads

Some people are too closed. They only hear themselves speak.

I disagree