It was a bug, because it made melee too powerfull in a First person Shooter game.
Nope, it just made provision for a playstyle that people didn't like getting killed by. The melee runners didn't often get great K/Ds, so the tactic in itself was not too powerful or successful enough to warrant it being legitimately called a technical mistake.
Also, I find that people try and use the genre argument too stringently. It's a game, you are provided with tools to get the job done, go do it.
I fail to see what's wrong with going subjective reasons on a discussion forum.
It makes for a 'my dad could beat up your dad' argument. You are trying to expand the definition of the term 'bug', as well as justify slurring successful gaming under the term 'cheap', which in itself is an ambiguous word in this context. It is absolutely unquestionable that camping is a successful tactic when done well. It has been proven time and time again. I personally fail to see how you can even subjectively justify calling a successful gaming tactic cheap, when it breaks no rules, uses no glitches and uses no 'bugs' (Unless you want to include guns under your new definition)
Camping is considered cheap by a fair amount of people. I, personally am capable of countering camping without too much difficulties. It's that a lot of people get caught soo easily by it that it's sometimes ridiculous.
Most people are capable of countering camping if they play intelligently. Grenades are but one option, staying away from that area is another. If you would discount the skill of finding a good camp-site, you cannot deny the idiocy of people running to the same spot time and time again. Theoretically, if people played intelligently, a camper shouldn't get more than one kill on each player before being forced to move to get more kills, or being killed by a grenade.
Once again, I'll point out that I'm not an advocate of camping, I simply despise the trend for people to put down tactics or skills which, despite being perfectly legal within the perameters of the game, they have no answer for.