|Probably too much.|
The "double logo" clause can apply to multiple articles of clothing of the same team, or different ones. Wearing your Bruins hat with your UNH hoodie is just as bad as putting on two Red Sox things at once.
Now obviously there are some exceptions. Layers is the No. 1 case against the rule. If you're going to the game and you want to make sure you're always displaying your team's logo regardless of the weather, I totally get it. It's fine to wear one under the other as long as only one is visible at a time.
There is also the "big game" exception. This has two parts:
A) If you're going to a game and having the chance to see your favorite team live is a very rare occasion (like once a year or less), I understand why you want to show your pride by getting all decked out--but there's no need to be putting on a full Patriots uniform every week. And even in this case, you're still probably better off just wearing one logo.
B) Playoffs. Everybody gets extra pumped up for this, and rightfully so. But it also has to be taken on a case by case basis. For example, this afternoon's Patriots contest is not that big a deal (unless you combine it with corollary A from above and have the uncommon opportunity to go). The Pats make the playoffs every year, we expect this game to happen. If it was the Bills hosting a postseason game it'd be a different story for their fans getting dressed as they head out to the bars today. But if New England makes the Super Bowl, then it's probably OK to waive the no double logo rule.