That comparison doesn't really apply if they don't buy those games (and thus label themselves hypocrits). That was almost a valid arguement.
I think the point that the boycott is supposed to be making is that L4D2 is what L4D1 was supposed to be. There's a distinct difference (all be it limited due to the shit, redundant genre that is sports games) between Fifa 7 and Fifa 8. Fifa 7 was not advertised to develop over several months to make your money go further. Fifa 8 is made to more accurately represent the football league tables and player performances of the year. With increased graphics, physics, animations and GUI.
Whilst L4D2 does feature new weapons, maps and characters, comparing it to a shit, redundant genre of games does not justify the circumstances of L4D2's release.
If the developers of Fifa 10 promised a game that accurately applied the hot and cold player streaks throughout the current football season, new manager take overs, team funding and construction of new football pitches via monthly DLC (or what ever). Then you had 1 mid season DLC that updated players with booking stats, and at the end of the Season Fifa 11 is released. You would probably get a boycott of that too.