Terrible tag idea, it's implicitly negative and accusatory. In this instance, the guy was apparently just honestly misinformed.
The main problem is that most of the original thread ballooned with upvotes because it became general "<big corporate entity> is bad" kvetching which is perennially popular and probably doesn't belong on HN at all. As long as these kinds of threads aren't modkilled, these things will happen, you just have to deal with it. Tagging them won't solve anything.
Technically, it is not known what the consequences of an untried action might be. There are many possibilities, that vary according to differing circumstances.
The main problem is that most of the original thread ballooned with upvotes because it became general "<big corporate entity> is bad" kvetching which is perennially popular and probably doesn't belong on HN at all. As long as these kinds of threads aren't modkilled, these things will happen, you just have to deal with it. Tagging them won't solve anything.