First of all this is non-merit discrimination; which should bar yammer from doing business with government, and contractors. Check out their fron-page, the top of their customer list is Pitney-Bowes.
Second, he is creating a hostile work environment for his own employees who may feel differently about the case, or who have come from companies that collapsed as he is expecting Yahoo would.
I think he's saying that it is an issue of merit, in the sense that he considers it a negative indication of the judgment of an applicant.
Hostile work environment? Meh. Sure maybe somebody could bring a suit, maybe they could even have a chance at winning if he was beating people on the head with it every day. But I doubt many startup execs would worry about it to the point they would let it censor their behavior.
Second, he is creating a hostile work environment for his own employees who may feel differently about the case, or who have come from companies that collapsed as he is expecting Yahoo would.