Generally speaking, picking on and bullying newbies is a Bad Thing™.
What happens is that a player with some amount of skill will knowingly challenge someone they know to be a beginner. Challenging is a feature that makes the whole playing scene work, but this does not mean that you should feel entitled to challenge whosoever you wish; someone who challenges knowing they will have an easy win must be aware that this will basically prevent anyone else from enjoying the game.
This is the fundamental problem with the chicken. Because of the prevalence of those who would seek out a victory rather than a challenge, many would-be players just give up; this phenomenon is considered partially responsible by many for the overall decline in fighting games. Then again, griefers will exist no matter what you do.
Obviously, organizing players with mismatched skill levels has always been a problem in competitive gaming, but certain games have introduced a ranking system (like the Tekken and Virtua Fighter series, which have ranks something like the kyū/dan ranks in modern martial arts). The problem is, of course, that defeating a low-ranked player will not raise your rank by much with these systems.
When beginners play each other and a skilled player challenging one of them becomes unavoidable if the skilled person is to play, there is an opposite problem where the beginners are being inconsiderate of people they could learn from.
For one thing, non-beginner players may be forced to wait around, and even though more and more may show up, they may have to wait a long time just to be fair.
The prevailing view among veterans is that this is a necessary evil, because as much as they would like to enjoy the game, fresh lifeblood is important to the overall scene. However, for new games, lines can get very long, so beginners and advanced players alike should be considerate regardless of skill level, and lay off bad and/or stupid antics.
The moral of the story? Give it your best shot, and don’t hog the machine.