I seem to remember past seasons when people agreed to an alliance of a final five (or whatever) with the caveat that when they got to that point, it was every person for himself/herself. I think bringing honesty, integrity, religion, and "family" into it is why the jury wasn't happy with Coach. Or Albert, for that matter, particularly after he took the immunity necklace as an act of faith from Brandon and then turned around and helped blindside him. And yeah, it was dumb of Brandon to be that trusting, but he really, truly, naively believed that Coach and Albert shared his beliefs, so it came off rather as if they had kicked a puppy. I don't think that helped them with the jury, many of whom seemed fairly protective of Brandon.
If Coach had just agreed to keep up an alliance with the understanding that at the point when they had to start turning on each other that all bets were off, I don't think people like Rick or Brandon would have been nearly as upset. Realistically, you might as well start alliances with that understanding, because at some point, all alliances of more than three have to break down, because you're forced to vote people off whether you want to or not.
What's ironic is that what Coach used to hold his alliance together is probably what ultimately cost his the game. Sophie stayed true to the alliance until she didn't have any choice--and I'm sure she and the rest of them would have been happy to vote out Ozzy instead of Rick if they could have--and had to fight for just herself. Moreover, though she participated in the prayer circle stuff, she didn't make any claims about honor guiding her game. She talked about strategy, not integrity, and she did far less lying to others. She also admitted her faults and where she made mistakes in the game and what she regretted doing when the jury asked their questions. That had to help too.
It occurred to me just a while ago that if Sophie just graduated from college, she's not that much older than Brandon, which makes her not necessarily understanding that others could take her approach as cold or bitchy more plausible. She's really young yet, and science departments (I'm assuming she majored in something like biology and chemistry) can still be rather "old boy" insistent on being analytical and concerned with results rather than emotional reactions. She may well have been unaware of how others might perceive her directness. However, Whitney calling her out on it, considering her own behavior on the show, was beyond the pale. I'm not sure I'd want to be all that chummy with Whitney either, so I get why Sophie may not have wanted to spend a lot of time with her.