I think that deep down nobody really has a problem with balance, balance is a necessary part of games, or they wouldn't be games, nobody wants to feel really useless all the time after all. However balance can be and usually is an issue, but not for the obvious reasons, deep down nobody hates balance, most of the time when someone complains about too much balance, balance isn't the real issue at hand, but the most immediate sign one can perceive of the real issue: too little tolerance to variance.
Which is the reason 'Balance is bad', too much balance can imply little room for variance, and usually it does (but it doesn't have to).
On the flip-side I've seen many people complain about too many options (option bloat), because too much variance can upset balance, and it usually does (but it doesn't have to). However it is actually the same issue, most editions of D&D have little tolerance for variance on their balance, they just choose to privilege one or the other, or just take the ball and run with it:
4e decided to be upfront about it and removed a lot of variance to preserve balance (and to sell more books too, you can only convert a very reduced subset of core-only 3.x characters using core-only 4e, the amount of core-only 3e pcs convertable to 4e increased over time when more splats and dragon issues showed up, though a few corner cases -and a lot of splat pcs- were never convertible. This compared with the 3e phb, which is enough to convert the practical totality of 2e phb characters, some complete book characters, a few AD&D characters not present in core 2e, and on top added new kinds of pcs not seen before), 2e on the flipside just kept on adding variance balance be dammned, 1e and 3.x had meassures of balance, but those got blatantly ignored by a bunch of the playerbase: Ad&d appraoch also focussed on reduced variance but most groups played outside the ideal circumstances, 3.x instead got one dm guideline blown out of proportion while the others got promptly forgotten in turn causing an arms-at-race of power creep that left balance in the dust while we kept getting more and more variance following the tendence set by 2e, though IMO this was a case where they weren't interrelated.
Just to be short the reasons some of us "hate balance", don't have to do so much with balance itself as with losing character variance in the process. And the opossite is also true.