I'm going to introduce my ex to my current sexual partner.
Why do you want to introduce your ex and your sexual partner?
Because he's such an idiot and such a loser, I bet my current partner would laugh at him.
I see that you don't think very highly of your ex, but you shouldn't go out of your way to make fun of him. Your current partner may think that you would do the same to him someday also.
What's he going to do? Break up with me?
Maybe, because it can be very hurtful to to your partner that you are still thinking about your ex. I think it's best to move on from that old relationship, and look forward to this new one without any feuds.