For a long time after starting out in a game, I think that every gamer goes through what I'd call their "scrub" stage. They think that, since they died, they have the right to call the effective tactics that took them out "newbie" or "cheap". This often indicates a depressed person is trying to play a game with a fragile ego. Everyone has moments like this, so I think that it's forgivable.
It's easy when you're new to come up with some code of play honour that says "this weapon is too cheap, so I won't use it", but this has a bad effect on both your chances of winning and of enjoying the game. More importantly, there is almost never a set of rules followed by the pros in a game that says which weapon they will or will not use. This is because of something we call the "meta game".
In Half Life 2 Deathmatch, the game the OP mentions, the RPG is often considered "cheap". But a pro will know how to counter the RPG, by nade cooking, bhopping up close and shotgunning, or using any number of other advanced strategies that almost always work. The RPG isn't "cheap" for these players because they've found its weakness (that is, its limited ammo, the long period between shots, and how suicidal it can be at close range to use). This is the meta game, when we find a layer of advanced moves that change the tiers and powers of each weapon, often coming to the conclusion that, surprisingly, while this RPG might work on noobs, the (in the scrub's view) more noble SMG or crossbow might do the trick against pros.
Scrubs are often newer players, because their attitude suggests that they haven't caught on to the meta game yet. They assume that the game is simple: you have the RPG, therefore you win. Game rules almost never are that simple, unless you're back in an ancient, stringent, turn-based board game like chess.
We all play better when we learn to say "nice shot", and "good game" to our opponents. We play better when we're confident and not taking the game too seriously, as this allows us to waste less energy on emotion, and more on aim and concentration. Unless they do something ridiculous that shouldn't be possible like shoot you in T spawn from B in de_dust2 in Counter Strike: Source. In that case, though, there's always saying "good game" and changing servers, or taking a break. If you get angry with cheaters and trolls, you just feed their ego. Stooping to their level is unhealthy for game communities.
To answer the OP's question directly, I've heard people call almost every single weapon in HL2DM "cheap" and ask me not to use it on various occasions over my three plus years of play. If it were up to the scrubs, we'd all be fighting with those very bad pistols, with no other weapons available. But then these people would cry "cheap" if you had the intelligence to blow up an explosive barrel they were obliviously standing next to. So you can't win in a scrub's code of honour. It's better to be pragmatic and play to win. And enjoy the screeching.
