It deserves a MM playlist as much as any other Custom Game along with any Forged Map. I do think that Swat is a much better choice than Grifball, because it takes more skill in my opinion, as Hammer duels are more random than not. An MLG playlist would be very interesting, as well as a Hub for "Hyper Competitive Douchebags" to screw around in(yes that is a proper noun). But if you don't want to play Grifball, just don't play it, don't whine about Bungie giving some people what they want, and not others. Not everybody can get what they want at any one time. I would prefer a more competitive style playlist, but since there is going to be some Swat, I'm happy.
Team SWAT involves no shields or motion sensors and battle rifle/magnum starts, body health is slightly increased but BR and Pistol headshots still kill in one hit. This creates very tactical and communicative gaming. Back to Grifball, I think it was a right decision because Bungie realizes not everyone has the opportunity to play large custom games with over 6 people, all requiring the map pack. This is much fairer because it lets people play Grifball who may never have had the chance in customs - like me xD