If you send the link with references of big party users, and under the premise that you can make it look as professionell as you need it to be, and you still get the „lol“s for a lol-TLD: show them the finger and let them drown in their traffic.
They were not interested in your opinion from the get-go.
Edit: anubis even offers a commercial, unbranded version.
Edit 2: Maybe the confrontation isn’t as harsh and the coworker sees a .lol-domain for the first time and is honestly surprised. We don’t know history and tone.