On the drinking thing, some of the 9/11 hijackers attended a bar in, I believe, Miami, even though others in their circle were vehemently critical. If I'm not mistaken, a few of the hijackers even went to the bar a couple of days before the attacks. Typical duplicity, putting down American vices and the open sexuality of women yet availing themselves of it.
Many of them also frequented strip clubs - in Florida, Las Vegas and elsewhere. one of clubs was the 'pink pony' in daytona beach, fl, days before the attacks. Some of them also reportedly watched pornos in their motels on Sept. 10 (according to the motel bills)
I 100 percent agree w/FOMW that Harris' offer is a possible out for Tony. Even if not via the terrorist route in particular, it forces Tony to consciously confront the possibility of flipping at a time when he's already worried about what the future might portend.
I took his jumpiness and subsequent anger as a sign of just how on edge Tony really is these days. I think the Tony of past seasons would have done a better job keeping his cool.
As Fly pointed out, Harris and Tony have a long track record. Also, from the beginning of the series we have seen Tony do a masterful job at staying level headed, albeit often a smartass, when the Feds came around. ( we've seen him shooting the breeze with Harris in front of Satriale's many times; waving and laughing at the Feds parked outside his house in season 3; etc.)
IMHO, a younger Tony (pre 'members only?' would have been startled at seeing the car pull up, but would have quickly composed himself when he saw who it was and maybe even smiled going up the driveway, feeling relieved it wasn't a more serious visit and maybe even flattered at the idea of being called upon to help get the 'real bad guys' (not that he would have done it then either -- but I could still see him liking the idea on some level) Instead, he looked extremely and unusually frightened, fear that quickly and predictably turned to anger.
I don't even think the dig at Meadow's safety would have set him off to that extent in past seasons. Sure, it's a horrible thought but extremely general. The example they gave doesn't put Meadow in any more danger than the rest of the population.
Finally, there's no way Tony would knowingly protect terrorists (remember how angry and concerned he got after seeing the '60 Minutes' special about the vulnerability of U.S. ports?) There are ways that Tony could indirectly tip off the feds and not have to technically consider himself a rat. We've already seen that he's willing to go the law enforcement route when he thinks the situation calls for it (the soccer coach, Feech) The feds' offer touched something off in Tony that goes much deeper than ratting out potential terrorists.