I'm not sure whether I think Sam was protected necessarily (though yeah, Dean took a lot of Sam's crap for him and shielded him from a lot of the ugliness of a) their life as hunters and b) John's frustration, which let Sam kind of decide what degree of involvement he'd have in hunting and training), but yeah, he definitely has a different sense of what family means, whether they have a duty to hunt just because they know what's out there, etc. As you said (very well), Sam can be selfish and selfless within the same 20 minute span when it comes to his family.

Thank you!