I'm sorry that it didn't work out. While you are entitled to, and I support your right to place any deal breakers into prospective relationships you wish - why is dating someone else a deal breaker ... well, I was about to say "this early into a relationship" but it isn't even a relationship yet so I'm not sure what to call it. Perhaps 'exploration'?

I am not judging you in the least, please believe that, but I am curious.