The people for whom it is intended view it that way. The idiots that put it up may think it's a sick, twisted joke, but for thousands of African Americans, it's grim reminder of not so long ago American history.
It is not the bigot who best determines how insulting, degrading, humiliating, or threatening such an act is...but the victim. If you were slapped in the face, who would be the better judge of how much it hurt, you, or the person issuing the slap?
Yeah but we're not talking about a slap in the face, we're talking about a piece of rope in a tree. Who would be the better judge of why someone put it there -- the guy who put it there, or a passer-by? Just saying, the logic doesn't really hold up.
We're talking about bigotry and who it hurts, and who it keeps down...so yes, it does apply. Just because the logic of my analogy escapes you, doesn't mean it doesn't hold up. Just means you don't or don't want to get it. The point is, if you are in the majority, or in power, the bigotry of the minority is merely an annoyance. If you are in the minority, it controls and throttles you. Whites (if they are in the majority) typically don't see prejudice or bigotry as a big thing, because for them, it really isn't. The minority has little influence over them, relatively speaking. It's quite different when you are the minority.
It seems that in addition to my "logic", the symbolism of a noose in a tree escapes you as well. If you were a black man in the south, you would feel quite differently about a noose in a tree. See how one side dismisses things, while the other takes it more seriously?