Cailin, I think you are being encouraged to read books on this because it is the case that cliques and actively exlusionary behaviour do exist, and you seem to be asserting that they don't, and that all instances of apparent cliquishness are actually quite alright and explainable. Given that social scientists have put the work in to write about this, and given that you might find it easier to take it in when quantified rather than the dismissive "lack of social skills" hand waving that can wave away anecdotal accounts of people being subject to nastiness and cliquiness, it might help you to read them.
It might be the case that you have never come across or noticed genuine cliquiness but it does exist and I think there is a level of frustration from some that you appear to be insisting it doesn't.
What is odd about this is that you make it clear that you are quite proud of not being cliquey - you have repeatedly made it clear that you could never be accused of anything like this, making the effort at toddler group even when you are not well etc - yet at the same time as highlighting this as something which takes effort and is to be proud of, you seem to be implying that the opposite never ever happens, oh no, never, not by you, nor by anyone else. Make your mind up, which is it?
As with everything of course, so many cases are a case of 6 of one and half a dozen of the other - but that doesn't mean that cliqueiness doesn't exist. It does.
On another subject - CBT - I believe, giving it the benefit of the doubt, that done properly it doesn't try to make you believe things that aren't true. However, as hunreeeal says, I think it is very often used to discredit genuine concerns and for some patients this is very very bad. I think where guilt is a part of depression CBT, done in a certain way, is actively harmful because it can be "heard" by the patient to be sending messages like: it's all your fault; you are seeing things wrongly and you are wrong; if you worked harder to think "right", you wouldn't be like this.
There is some research that shows that statistically most people over estimate their talents and attributes, ie, something like 80% of people believe themselves to be above average at social skills. This is of course statistically impossible. Depressed people tend to have a more realistic view of things. I think rose tinted glasses are perhaps a necessary part of being functional. But it doesn't mean that arguing yourself into seeing rose-tinted means that you are seeing what is really there, and the loss of authenticity required to do this can in itself be pyschologically damaging