1. petitions don't work. this is coming from the guy who's approach was the premise for the at&t and vzw petitions.
2. at&t and vzw mandate the locked boot loader, NOT Samsung. they do it because of $. NOT because of their stupid services or apps or search hits or whatever tinfoil hat speculation prevails this week. they do it to minimize warranty claims. you buy from the carrier and the carrier bears the warranty costs.
3. point 2 is best evidenced by the significant increase in "halp I froze/deleted/modified/tweaked/xposed a bunch of stuff and Noe my phone doesn't wurk right" or "bad user experiences after root" threads. root didn't do this to your phones, you did. good thing these mods probably tripped the Knox counter or we'd all be paying that cost in the S6...
4. if you got the phone on a 2 year contract or a next plan, you did NOT buy the phone, you are basically financing or leasing it. up until that point that its paid off, its not yours to do as you wish.
5. if aosp/cm/aokp/pa/countless other baked/tweaked/modified/themed Roms is your thing, do your research and find out if the phone you want is unlocked or unlockable.
5a. aosp base Roms are nowhere near as good on a Samsung device as they are on a nexus device, too many other closed source or proprietary things going on with Sammy's. this isn't a knock against our developers, they are pretty freaking awesome for being able to reverse engineer this stuff well enough to get a working ROM. nexus is better though because it was BUILT for that.
6. carrier bloat can be frozen on an unrooted device., plain and simple. the stuff is there but you're not forced into using it, you can freeze it from the app drawer in about 30 seconds in one shot.