Not really, but think about it for a moment. You have a team of four to six people, and this guy runs out once to accumulate a small score, and then spends the rest of the match sitting in the locker room. Now, what's so bad about this?

For one, that team is now undermanned, playing against a fully manned team. The consequences? Less overall damage output, meaning that the opposing team has one source of threat out of the way. Longer capture times, meaning that you lose one individual's worth of capture time. This could easily make the difference between win and lose. Overall, being one man short can cost your team dearly. Fortunately, this isn't always the case, but unfortunately, it has grown to become such a problem that this issue is being brought up in public as seen in this thread.
The unfortunate team-mates of this leecher will have to work for a second man's worth, which is extremely tough if the teams would initially be on even terms of strength, even harder if not impossible if the opposing team has a star-player.

So while you are working your bones weary to win that game, that one guy who sat in the locker room letting you guys play his game reaps the rewards while only having to show up briefly on the battlefield. Remember that the disqualification system was implemented to make players actually fight instead of AFKing for their rewards, and this is but a loop-hole to get away with such degrading actions. Oh, and let's not forget the most important point of all; it ruins the fun for the other players. The point of the game is to have fun, no? If a player takes the fun out of others' enjoyment, then isn't it fair that they get punished for doing so? This is standard MMO etiquette and I support the ability to strike judgement upon these players.