I mentioned in my first comment that I think there's a lot of uncharitable parsing and cherry picking going on, all around. I think that's going on here, just as I think that's going on in a lot of political discussions, and it's obscuring a lot of very real issues that people generally agree on and increasing polarization.
I'm getting that impression from you in this discussion as well. Given the email as a whole and his follow-up, I don't get the impression of a CEO that would have someone fired over either of the T-shirt examples you've given. So far in this thread, that's been implied by your argument, and that's the only thing you've put forth. I also don't think that's everything you have to say on the topic, and I'm not going to assume what that is. Building straw men is in no way a useful exercise for constructive discussion.
I think there's a lot to be said for your statement:
"Social commentary on the current attempt to render expressions of affinity for one's "cultural background, language, and heritage" as socially unacceptable, and indicative of regressive and/or antisocial mindset"
I also don't see that being fairly applied across the board by a lot of people making arguments like this.
As stated before, I don't know that much about GrubHub or the CEO. If there is other evidence based on his behavior or experiences at GrubHub, that would add to this discussion of the letter and its affect on GrubHub. As I don't have any, I don't have anything more to say on the topic.