I don't like that they've done this, but I get it.
Groupon and Living Social are basically mechanisms to market some sort of group or couples activity. This means they predominantly target the dating scene. 50% of their customer base is women, 25% of their customer base (or more) is wussified leftist males. Probably more than 25% because they predominantly market to urban and suburban populations.
Of the 50% that are women (remember these are also urban women, same bias here), maybe 10-15% are reasonably pro-gun.
But, they do have 25-40% customer base that are pro-RKBA, presumably.
So it's a recipe for an awkward date or group outing in the wake of a mass shooting.
The intent of these services is to act as a sort of social lubrication. That doesn't work when there's national tension over something like Sandy Hook. They're not likely to sell much of whatever the gun-related service is due to their demographics, anyways.
I haven't heard anything about Living Social doing the same as Groupon, but I will contribute to a boycott of Groupon. If Living Social goes the same direction, I'll boycott them too. Just makes dates or outings a bit more expensive, not a big deal.