What makes you so sure? Just because you 'feel' you are experiencing consciousness doesn't mean other people are. How do you know other people are? By means of objective perspective from your subjective one? By doing so your consciousness already reached out into the material world and so you only validate materialism by acknowledging the presupposed immaterial consciousness of others.
Honestly I don't think either materialism or immaterialism can be argued for without contradictions of some kind because one (immaterialism) argues the validity of the subjective experience while consequently delving in objectiveness, the experiences of others, any time you have to argue its point and relating it to others. Materialism as you, or someone else argued, is rooted also in a subjective experience so materialism can't discount the immaterial either.
But why be either/or? Why can't both be valid? Because humans like to argue, I'd say. We like to compress information and when there's contradictions, we can't validate both because that kind of information doesn't compress well. Same reason we have to find one side to blame, it can't be both sides because that's just too complicated.