It can be pretty difficult to accept, especially when the problem is some fundamental aspect of your personality rather than something easily addressed like hygiene or fashion sense. And when all the feedback you get is either non-informative or is critical of the wrong things, it is very difficult to even figure out what you are doing wrong and how (or whether) you can change it. As a culture, we’re conditioned not to admit fault even when culpability is clear, much less when it may be subject to interpretation.
Most men either learn the appropriate modes of general social interaction early through strong family and social bonds and intuitively apply the appropriate modifications of those modes to dating and romantic relationships, or they don’t learn them at all. And unfortunately there is very little practical guidance for how to pick up those skills later in life, especially if you have a social handicap such as not being able to read emotional cues. As dysfunctional as the self-proclaimed “seduction” and “pick-up artist” community is, it is at least trying to present some kind of education on adult socialization, which is what their clients need. Unfortunately, the “coaches” who practice this trade are largely limited to teaching initial pickup techniques that largely work by plying on the insecurities of the women they are targeting rather than the large scope of social interaction in general or even the gamut of skills necessary to build and maintain an actual relationship or deal effectively with the inevitable conflicts and demands that being in a long-term romantic relationship entails.
Whether you are a self-described but passive-aggressive “nice guy” or just a “decent, albeit (socially) clueless man”, it can be difficult to get past the barrier of not meeting the requisite set of expectations that the vast majority of women (quite reasonably) have and getting far enough into dating to even learn how to stop doing things wrong. The same is true, I expect, for physically unattractive women, except they have the additional hindrance that their “deficiencies” aren’t even superficially concealable with bluster and bravado.
For the o.p.'s sons, dealing with the social anxiety (and letting them know that they are loved and respected regardless of how the world at large treats them) is probably the best he can do. Encouraging them to develop interests in some kind of outgoing activity with social opportunities to interact with women of comparable age, e.g. team sports, volunteering, debate/mock trial/Model UN/whatever, will maximize their chances to come into contact with women on an extended basis so they can get past the initial social awkwardness and display confidence in an activity.
Stranger