If it was just one torpedo, or if they fired on us any other way, that's good enough for me.
I've read accounts that vary, too. Just because somebody with a book or article for sale has an axe to grind, doesn't mean they have checked their 'facts' thoroughly. The only people that know for sure are the people that were there, and even they may have seen varying pieces of the picture, or --guess what -- their viewpoints may have been influenced by their politics over the war.
Remember, it was the cold war, and at the time there was the "domino theory" where it was believed that if we let one country fall under communism, the whole region would become Russian satellites.
If you can find a library with a collection of Vietnam magazine, you should find somme more information. Especially the book reviews, which have in some instances been sympathetic to some pretty hostile and poorly written books, even though in general the tone of the magazine is supportive of the men who fought there.