I agree with you about assumptions...But I think it is a completely different matter when you start discussing celebrities lives/sexuality... If I saw you walking down the street with your girlfriend and/or boyfriend I wouldn't assume anything. (I would check you out, but I wouldn't assume anything

) But this would be because I don't know you or anything about your life....
With celebrities there are certain aspects of their lives that are common knowledge - likes, dislikes, backround - garnered from magazine articles, television interviews etc. So we begin to make assumptions on things we don't know (sexuality in particular!) based on the things that we do (where they are seen, how they dress, comments they make etc.) They stop being assumptions and turn in to educated guesses - or more often than not wishful thinking!