Muslims acknowledge the man, because he's rather central to their faith. Muslims denouncing Jesus would be like Muslims denouncing Muhammed. It's not likely to happen.
Jews... Might out of some sort of politeness.
But it is certainly NOT 'written of in many roman texts.' If it were, you could find a source for me that proves it. The few snippets that exists are fake, however. Does this disprove the existence of Jesus of Nazareth? No. Does it prove it, however? Also no.
You should read the rationalwiki linked above (by PRE 9-11). Whether or not he existed is not the important part of this, however. It's a religious debate because there is no evidence that he did (unfalsifiable claims and all that), is a strongly religious figure (undeniable), and is the figure central to the author's beliefs. Furthermore, the story is politically focussed hogwash full of confirmation bias.
Again; look at the links provided to you. Compare information, writing styles, arguments. Deduce from causalities rather than gut-feelings.