Of course Goodell could ban him.
As for Glazer giving up his source, of course he doesn't have to. That doesn't mean he shouldn't suffer the consequences of that choice, though.
Belichick doesn't have to discuss anything with the press. This past week he suffered the consequence of that when the media mounted a witch-hunt. He then chose to not discuss any of the fallout with the media, which he will no doubt suffer the consequences of in the future.
(I loved Dr. Z or SI being so upset because Belichick refused to discuss it, saying he should have to come clean blah blah blah. He totally ignored the fact that Belichick only had to come clean to the one person who actually matters, Goodell. The media can't deal with it when things aren't about them.)
Sometimes one choice you make for your job affects other aspects of it. Glazer chose to come forward with the tape, and if he chooses to keep the source of the tape secret he deserves the consequences.