BB,
I admire your passion and desire for Scarface. I too believe it is a great film, much more deserving than the 2 stars it got.
As per the violence aspect, I believe that, at the time, it was considered gory and too violent. But by today's standards, with all the new technology available for horror films, Scarface should be rated PG. So I think it is all a matter of the age the film was released.
And as far as insest goes, no way. He was just being way too over-protective. As Manny said, Gina was the only thig "pure" in Tony's life, and Tony wanted Gina to stay "pure" and not get caught up living with someone who is in Tony's business. Now, realistically and off-topically, Manny probably would have been a good husband for Gina. From what I saw of Manny's character, he would have been the best match out of all the people Tony knew.

As we agree, Scarface is a classic that was judged pre-maturely.