That all comes from the defender mechanic. If the fighter went off and just attacked things like a 3rd edition fighter and didn't use it's "defender" mechanic then the fighter would be looked down upon because it didn't use it's main ability.
I was just saying that I know of someone who just stood there and acted like a bodyguard.
There isn't any 4e defender mechanic that rewards standing near your friends and not attacking or at least engaging the enemy. If a 4e fighter goes off and attacks things like a 3.Xe fighter, they are setting themselves up to actually use their defender mechanic. I'm not sure what is meant by "didn't use it's [
sic] main ability." That can, as I understand it, refer to one of two things.
It might mean that the fighter didn't apply the mark when he attacked, which can have some validity if the fighter is, for example, low on hit points or surges and the rest of the party is healthier, but would otherwise be a tactical error. The other thing it could refer to would be not taking the provoked combat-challenge-based attack, which would only be a valid tactic if the fighter had two things marked and ignored the (for example) minion's violation in favor of holding it for the upcoming brute's turn.
If the fighter does not apply the mark (without extenuating circumstances) or does not use the combat challenge attack that an enemy provokes (absent, again, extenuating circumstances), then yes, they would likely be looked down on, but only in the same way that a 3.Xe fighter would be looked down on for not taking a provoked AoO or making only two of his three possible attacks on a full attack.
The 4e fighter may want to strategize targets for attacks slightly differently than the 3.Xe fighter, but in both cases, the character should be attacking the enemy each and every round. Standing near your friend and waiting for the enemy to come to you and attack like a bodyguard is not being a defender. There is no "bodyguard" role in 4e. That they (the person in your example) chose a fighter is irrelevant (and, most likely, really sub-par for that job -- a striker with the guardian theme would probably be so much better).
Back in 3rd edition I had a Abjuration Wizard (Initiate of the Sevenfold Veil) who was was my Fighter's bodyguard so it goes to show you that any class can act the "bodyguard" role.
I just don't want that mechanic built into the class, I can do that on my own if I want to.
There is no "bodyguard" role in 4e.
The best 4e bodyguards that I've seen are, as mentioned, strikers (with a good constitution and a solid basic attack, like an infernal hexblade) with the "Guardian" theme from Dragon 399. I could see a similar idea (though not a Guardian theme) for a staff of defense arcanist wizard, as they at least are likely to have a good constitution for surges/hit points and a decent int-based AC. The particulars of the build don't leap to mind, however; it's counter to how I generally play wizards.