I think the question is more geared towards the fact that you already landed and therefore can't tell tower you're going around. I'd talk to the CA first and explain to him that while he may feel he can make it, regulations exist for a reason and you would like to keep your certificate. As a retired UAL captain once told us when a buddy met an undesirable young lady at the bar "If you're not going to abide by minimums, why even have them?"

If that doesn't do it, contact the PSC (AFETR you've talked to the CA and have told him your going to do that) at your company and request help. Get advice from them on whether you should fill out an ASAP report. The main focus is to keep it within the pilot group and solve the problem without hanging a guy out to dry. What they're generally looking for is that you don't say "I'm going to call the Chief Pilot and rat him out and hopefully cost him his job".