I have not read all 6 pages but I have read the last couple and some of what MikeUSA posted. It seems to me (and forgive me if this was already mentioned) that what is offensive to many people is the outright lack of respect that this action caused to be felt for those who served and continue to serve their country. Also and probably more importantly, to those parents, spouses, siblings, children and friends of those who died or are disabled and disfigured while serving. To lose a loved one in this manner is very hard and wreaks havoc on families.
I was always taught that to stand was to show respect and honor those who have fought for this country and serve to protect it and all of us. We all of course, have the right to do many things that are not against the law. People have the right not to stand. But I maintain they have a responsibility to do so - for all that died and were injured for that right. It shows respect for them and that (IMHO) is what this should be about. Those who served so we have those rights.