1. Only as a last resort...I prefer independent shops.
2. Starbuck's will not lose millions from their no-gun policy, ever, under any circumstances, period, end of discussion. You voluntarily disarming and showing up at Starbuck's means you consent to whatever meteor-strike possibility there is that you will be victimized. By your rationale, every persona harmed in a GFZ shooting has a legal claim against the GFZ landowner. Good luck winning that legal claim. Quite simply, and in most jurisdictions, a business is required to provide a reasonably safe environment for its invitees and is allowed notice/opportunity to correct dangerous situations (spilled water on the floor, icy parking lots, etc.). Most shootings don't happen with any sort of notice and businesses aren't required to ensure (or insure) against every imaginable risk...and they certainly aren't required to cover you because some crazy person shoots up their store. The lawsuits happen, and they get dismissed.
3. There are different kinds of requests and there are different relationships between requestor/requestee and there are different contexts in which these requests are made/granted. Your example is, to put it bluntly, irrelevant and stupid. Starbuck's has every right to post a code of conduct, or ask that its business invitees refrain from bringing dangerous items into their stores...yes...guns are dangerous items. Starbucks has had murders take place in their stores, and they still haven't said "hey citizens, bring your guns because it makes us safer." Are you suggesting that you carry your sidearm to keep strangers safe? I think that's a bit of a stretch and I don't know why on earth you would extend the benefit of your personal sidearm to protect strangers from bad people...that's a moral issue and quite charitable of you...but you'll lose your life savings defending lawsuits brought by people accidentally harmed (or properly harmed) by your actions and I suggest you give it more thought.
4. I don't think OC'ers are bad people or more dangerous...but Starbuck's has to have a company policy that applies to everyone in every situation and they can't take the chance of things going sideways. You're making a logical mistake in thinking that everyone is exactly like you...Starbuck's can afford to be wrong, especially when it's cheaper (from a risk standpoint) for them to encourage their employees to be non-confrontational. Believe me, Starbuck's employer/employee relationship has FAR more liability attached when a dead employee's family sues saying the store policy forced their loved one to confront an armed patron who turned out to be a nutjob...confrontations are for the police and should be left that way.
I'm not forcing anyone to do anything, but I suggest you take a serious look at why you carry and for whom you carry. Unless you're LEO, you're gonna be in a world of hurt if you pull the trigger...and that's the BEST case scenario. You may escape with your life, but your career will be in tatters and the lawsuits will come on strong. Consider who you want to endure THAT kind of pain to protect. This is way off topic but worth some thought.
Bottom line, respect requests lest they become bans/signs/laws. Open your own shop and post "guns welcome" signs...but don't disregard Starbuck's request simply because they tried to split the difference or said "it's not a ban." You better believe that in your trespassing case a judge won't look favorably when you respond "yeah your honor but they didn't SAY BAN!"