THREESOME...no thanks!!!

Last night, in conversation with a man I met online, he asked me whether I would participate in a threesome with him and another woman. After I declined and dismissed any further interaction expecting we wouldn't be conversing any more, he replied:

"I've done that a number of times. It's great. But it's not the end all of what I'm looking for"

I thought about this a second. Why would anyone shelve what they value for another human being? Clearly, it's an activity he enjoys. Why would he dismiss this to pursue something with me that does not include the scenario he vividly replays in his mind?

Some time down the line, this will become an issue. Why would he shelve his desires for a woman looking for a committed, strictly monogamous relationship?

Here's how this plays out for me:
I'm not shelving my desires or values for anyone. A match should be two people with similar interests merging and complementing each other. Sexual activity is a part of that. In this case, he'd lived out that scenario already but still hasn't satiated whatever desires lie within participating in that scenario. If he's willing to shelve that, he's only going to implode (no pun intended). Do I really want to have that kind of mess on my hands down the road of relationship?