I might be whacking a bees nest with a 4x4 here, but I'm curious. (Ha)
Ok, for the most part, Moonboots has it solid with the whole loyalty mission explanations (that he ultimately chooses, not Shepard, and the Garrus from that choice on differs but is THE Garrus of that playthrough/verse/whathaveyou.) I'll find the quote millions of pages back in a bit.
But for the most part, I know that my Shepard's attraction to Garrus's character is the whole 'we're friends because we think so much alike and it's awesome, man we kick ass' type... stuff.
But... I've seen it mentioned... do you guys really think that the whole Sidonus situation has 'broken' him?
I mean... I don't. I don't think Garrus is broken in the game, ever. I don't think he needs guidance or fixing or whatnot. Information, sure, which is why I always paragon the info out of Sidonus but let Garrus take the shot, once he's got all the facts.
I dunno. This could be over thinking things, but I hate the whole idea of 'X is broken only you can fix him' and that being the attraction to his character (it's sooooo not in my Shep's case.) Relationships like that aren't destined to last and I'd like the think that as two individuals that can see each other as equals, Garrus and Shep's 'ship can endure.
There is no tl;dr (god I hate that term.)
Also

I love when Garrus defends his involvement with the mission. XD