I don't think anyone thinks rocks are alive. I don't think "dead" a particularly good description for them either. For something to be dead, doesn't it imply it was once alive? I don't think rocks were ever alive. Having said that, of course there are exceptions, like lumps of coal for example. It might make sense to describe coal as dead matter since it was once living matter. But not so igneous rocks and so on.
We know that we experiece things and we know that we are made of matter. This is the only instance we have direct experience. So we know that at least some matter is able to experience, because we ourselves do. Which kind of poses the question: are there other kinds of matter that lack the ability to experience? We can't say for sure. Which kinds of turns the common intuition on its head, and suggests we should take the experimental quality of matter for granted, until proved otherwise in any given case. Or at least it shows that it's not necessarily safe to assume the non-experiential quality of matter outside the consciousness of humans and other species.