My general assumption is that men who use prostitues are creeps. However, you say this man is fantastic and so perhaps he is. If I were in your situation my actions would very much depend on how much I liked him, how much I trusted him and whether his use of prostitutes was a regular thing whenever he was single. If it was a regular thing I would no longer be interested in him as I would no longer consider him to be that fantastic. However, I don't know for sure, but perhaps if I really liked him, trusted that he would never use prstitutes while with me and if his use of them had been a one off or maybe even a consequence of an exceptionally, only could happen once, drink fuelled night, I could live with it. It really depends on whether you feel that you can live with it, if you can then go ahead, it would only ever be between you and him and so you wouldn't have to fear judgement for your decision from friends or family.