Warning: Wall o Text ahead.
Purely my opinions and conclusions. You are more than happy to point out, poke holes in and argue with them at will.

:innocent:

Alistair:
Hes a Royal bastard, raised amidst Nobility and then schooled by the Chantry and Templars.
What does that means.
Lack of self esteem coming from his childhood. Ever present knowledge that he's a royal bastard. Arl Eamon seems like a good man, and as much as he was Alistairs early father figure, I suspect he was also a somewhat distant figure to the young Alistair. Duty would have kept him at some length, then I'm sure Isolde's dislike would have ensured a certain distance.
Alistair craves a close loving family more than anything else, which has been shown in the Desire demons dreamscape for him.
Being then carted off to the Chantry would have probably crushed the young boy to a degree. Torn away from the only home hes ever known because his possibly only known mother figure hated the sight of him. Then picked on at the Chantry for being, 1. a bastard, and 2. a bastard with probably some nobles habits due to being raised amongst such.3 Said nobility keeping a watchful eye on his tenure during his time at the Chantry.
Could possibly account for why he kept such a grudge against Arl Eamon up as a child. He felt angry, betray, resentful and most tellingly probably abandoned and unloved.
Destroying his mothers amulet's probably another sign of his intense feelings of abandonment. First by his mother dieing , then by the Arl.
With all of this, its probably not surprising that with his intelligence, that he developed a sharp wit and tongue to keep others at bay and to mask his own feelings under humour. Also where he became content to let others underestimate his intelligence, as people are often threatened by those smarter by themselves, and always willing to underestimate those that appear dumber than themselves.
Look at the Chantry.
Raised probably in a predominantly all male environment. Possibly open to abuse, but by the sounds of it, Arl Eamon made frequent visits which I'm sure let everyone know Alistair had a high powered guardian. This would have allieviated any major abuse, but probably not the small things, like the tormenting any normal children can do.
He was essentially raised as a warrior monk. Templars probably being one of the primary means for a religiously minded male to take up orders as such, since the Chantry seems to be predominantly Female. Raised into a mindset like the romantic authurian knights of old. Gallant, attentive, romantic, forthright, honest aaaand Chaste.
Still essentially good natured and king, so he didn;t develope further bitterness, but instead let himself be involved in Chantry teachings and learnt to enjoy the learning and discipline of being a Templar trainee.
Again being raised in an all male environment has meant hes had little exposure to women willing to flirt to any degree with him, and what few women hes seen hes probably been Chantry priests and superiors who would have schooled him in the knightly graces and arts of nobility. How to be courteous and reverent. He's been around women he's been raised to respect and converse with as an equal, hes been raised amongst men for whom being chaste isn' an issue of shame, such as it is probably a point of honour.
However he's still hung around in an all male environment and boys will be boys even when their old enought to know better.
So sex has probably been a hot topic. Its probably happened between the various other males templars as well. In that enviuronment lack of sexual experience wouldn't be something to be ashamed of, so much as simply par for the course. However being who he is and where he is, since he's (probably) not interested in men, its not something he's going to partake off and its going to stay an interesting, but distant topic on which he's not probably going to ever have any first hand experience off.
He's still not fit into the Templar life, having far to irreverent sense of humour to suit the more serious minded Templars, and probably too questioning of the Chantry really in general.
Then Duncan has appeared and whisked him away to the Grey Wardens....to promptly spend all his time again amongst more men. However these I'm sure are far more streetwise and world weary than any of the templars.
They will broarden his horizens and mind view even further. He will probably still get exposure to more women, however I'm doubtful the Wardens stay still long enough at any point to allow him to grow attatched in any meaningful way to any of them, since by this time hes well and truly under the habit of Chantry behavious towards women and wouldn't dream of entering into any kind of relationship other than a permanent one. I'm sure had Duncan had more time to wean him of some of his more odious Chantry leanings, this too would have faded in time, however....
Ostagar happens and he meets us.
So at this point we have One tall attractive, intelligent male. Well skilled in the arts of war and bloodshed. Capable and confident as a warrior which time with the Wardens would have only polished further since they take only the best. Raised in the best of Chantry and Templar traditions to be Gallant, Honest, Honourable, Chivalrous bleh bleh bleh...Being Alistair this all comes with a helping of attitude, hunour and a smart mouth to cover his insecurities.
No experience with women, and no shame about this. Embarrasment and annoyance at his own lack of knowledge are quite evident in those cut scenes I'm sure we've all watched multiple times, however.
Grey Wardens would have also by their nature encouraged his loyal self-sacrafising tendancies as well....
So we have the bundle of apparent cotradictions made manifest in one sexy as package named Alistair....