In women-dominated communities, it is a truism that this sort of statement is generally uttered by guys who are jerks but don't realize it.

That may be true generally; I don't date men. However, I know some serious past relationships have been destroyed by my being too nice and not sufficiently asserting my own interests. Women generally get put-off by guys who make a serious effort to cater to their every whim, regardless of the jerkishness of their motives, and a lot of guys fail to understand this. While there is certainly the strain of guys who are overly nice because they think it'll get them some, there are also guys out there who are genuinely nice because they obliviously think it will actually accomplish their goals.

ETA: There's a difference between "Nice Guys (TM)" and nice guys. The former are perhaps justly disadvantaged. The latter can often find themselves unjustly disadvantaged, and PUA does a lot to counter that.