It's not so much a problem with min-maxers that I see, as it is the traits commonly associated with them. Simply turning out a powerful character with a number of drawbacks (mins as well as maxes) isn't a bad thing... it's when there's a radical twist of min-maxing player taking extremes that problems show up. As a note, just about any player can do this... roleplayers can attempt to roleplay their way into doing things their stats disallow. Typically though, it's easier on boards to discuss the horrors of a 40 STR Large Tauric Half Dragon Monk Grappler rather than the Dex 12 guy trying to describe how he dodges incoming arrows for a bonus stunt AC point.
Anyhoo, here are a few examples i've seen of extremeee min-maxing!! (and the problems they entail which lead to hate for min-maxing)
1- Best or Bust: A min-maxer takes binary opinions on everything in the game and then tends to extend it into his idea of how dnd campaigns function. The values they place upon everything in the game are "Ideal/Optimal/Best" and below that "Worthless/Not Worth Consideration." With their own characters, they analyze their build and cull the inferior feats, replacing them with superior ones... and the superior ones are always superior and taken, while everything else is ignored. This then shifts over to a matter of "common sense" (who would waste a precious feat on something not perfect?) that extends into how they expect the world to function.
Example, someone who thinks that since a feat is suboptimal for fighters, that it makes sense no fighter would take it... alternatively, that every wizard should be an Archmage after 13 odd levels, or that typically there are few melee builds in the world without Fighter 2 as a minimum. The world then begins to pattern itself around optimal choices, and the expectations of the world drop from fantasy to probability and pure crunch. Numbers pervade the setting, and the players manipulate them (or try to) in Red Magician fashion (see 8 Bit Theater)
2- Limitation due to Optimization: A min-maxer who tends to think in "Best or Bust" lines of thought also tends to get in a bit of a jam when his characters die. Since there are only a few optimal builds per character purpose (like a dual-wielder), if one of his attempts at this path fails, he either has to recreate a nearly identical character or scrap the idea entirely and move onto the next character purpose. If he doesn't take the same ideal feats in the same pattern with the same class progressions (maybe varied her or there) he'll be sub-optimal. Overtime, characters die- and with that the potential for new characters ends, and the only option is to recycle characters (or play sucky ones.. which is not fun).
3- High Maintainance Gaming: Some min-maxers are also really high maintainance for their dms and this gives em (the DMs) a generally negative opinion of them (the min-maxer). This can come forth in any number of issues, be it "negotiations" for what's acceptible or not acceptible, or a constant review process over various feats, skills, and the applications and usages of those feats and skills. A min-maxer who takes his stats to the Nth degree can sometimes turn around and interpret those stats as loosely as he can get away with, getting as much out of it as possible, compromising play in some instances, or at least causing the DM to constantly monitor his gameplay. While it is understandable that a player wants to have what he takes matter, it takes a good deal of manipulation of the term "good sportsmanship" to constantly twist the language of the text or demand as much as possible in every way, shape and form and expect this to be acceptible behavior that a DM should permit (nevermind respect and encourage) on a regular basis.
4- Stepping on Toes: The biggest sin of all to some groups: some min-maxers invariably have this problem where they have to be better than others at the tables... not only in their own functions, but in the functions of others. Wanting a powerful character is fine; wanting an overpowering character can be dubious; and wanting a character more powerful than other players (even to the extend where that one character outdoes the others at their own niche tasks) is where the real issues can be sparked. It's pretty bad when the fighter is worked around to outdamage the rogue on a regular basis, or the cleric can always outshoot the ranger, or the dwarf never gets hurt ever, and he's not even supposed to be the party tank. When one character does the work of two, and the work he's trying to do is all another character has to offer... it can be off-putting.
In the end, it seems the biggest problem is not a min-maxer, but a selfish min-maxer... heck, any selfish player (it's just easier to point out issues with min-maxers without straying too far into the realm of pure opinion.. what with the numbers and all). Any player who expects the rules (and their interpretations) to bend in their favor, at their whim or desire, can be called, with no large stretch of the imagination, a bit of a problem. Any player who cares solely for what is on his sheet, and has no thought for the manner in which his character build can cause potential problems in a campaign, can be seen as a problem. Any player who doesn't give two cents for what's going on unless it involves a save, attack, or check, can be questioned in this regard as having something of a narrow vision when it comes to the expectations of your typical gaming group. When the ultimate concern is "me," then "we" can take issue.
