Dude, you shouldn't let his mind tricks get to you. Instead of walking ou ton the match, you should have kicked his ass and beat him 25 to 1.
And for the DLC debate going on now: I think Bungie is going to care more about players who buy the maps than those who just hop on Halo once in a blue moon who havn't bought the maps. From a bussiness perspective, the only players making Bungie Studios any money right now are those who actually buy the DLC maps. So you're lucky that Bungie isn't like Microsoft, otherwise every playlist would require the maps and force players to buy the maps.
But we know that Bungie is not evil and loves its fanbase and would never do that... right? I mean, it wouldn't hurt me though. I paid 20 dollars for maps so far and can only play half of them in the mainstream playlists.