If you wish to criticize the war, please do so in an academic setting, not at the site of a massacre and a memorial to the dead.
Honestly, this isn't something that I agree with. When I was in America (did six months of high school there) my host family took me to a lot of different historical places (I'm a history nut and so were they, it was a match made in heaven, especilly on the East Coast) At every place, inlcluding the Washington monument we discussed the differing views on each individual site. Now its its a grave (such as Arlington), or a specific part of the historical site that is a memorial (such as the Arizona at Pearl Harbour) than obviously you treat it as such. But walking around Gettysburg we chatted about EVERYTHING to do with both sides of the war. Hell, we sat on the Grassy Knoll and discussed Kennedy's politics! I honestly don't find this rude, unless its vulgar for the sake of being vulgar.
That's a great point. There must be a big difference between discussing different historical perspectives of a particular historic site, and making rude comments about how stupid people were for dying somewhere. I still have difficulty seeing how the former can be considered to be rude, but I'm willing to be educated. I would also think there would be a difference between a religious site, and a political site, but I'm not sure what I'm basing that feeling on.
For example, would it not be permissible to criticize the Vietnam war at the war memorial, or at in Vietnam, rather than in an academic setting only? In this example, I'm not talking about a rude criticism of soldiers, but a criticism of the justification and results of that war.
"All history becomes subjective; in other words there is properly no history, only biography." - Emerson
"The truth will set you free. But first, it will piss you off." - Steinem
As a history major, I study both sides of the history. I think there's a difference between a memorial and a historical site. I'd personally wait until I had left a memorial (such as the Vietnam war memorial) before discussing the negatives of the war, but I'd have no problem doing it while walking between that memorial and, say, Roosevelt's memorial. At a historical site (such as Gettysburg, though not in the cememtary) I think it would be perfectly legitamate to discuss all sides of the war, both positive and negative. The difference to me is that at a memorial is a set place for honoring and remembering people, while a historical site is that because a historical event happened to occur there. So, I'd criticize the war in Vietnam, but not at one of their memorial sites, nor at the U.S. Vietnam memorial.
I think both the positives and the negatives need to be talked about, but to do it in a place that is specifically and only for the remembrance of people who died is tactless at best, downright rude at worst (depending on volume and words used).
Also, rude, non-historically based attacks are completely inappropriate in my mind.
But... Is the Alamo only a memorial or is part of it a memorial and part of it a historical site? In my opinion, the behaviors are different for the two (I last visited the memorials in DC about 3 years ago). At a memorial, you are there to respect and honor the dead memorialzied there. At a historical site you are there to learn about the history of the place, and the events of that historical action, in the case of the Alamo, the Texas War for Independence. If it is in it's entirety a memorial, then any critical comments are probably not appropriate, but if there is a specific area that is a memorial, and the rest is set up like a historical site, then criticism (NOT saying unfounded nasty remarks, but historical criticism) is, in my mind, legitamate.
I've also noticed, as an observer, the older a memorial is, the more it is treated by the public like a historical site. (This impression comes from the D.C. memorials). I don't know how I feel about that as of yet.