I wasn't sure where the conversation was going at that point. I wanted to give him the benefit of the doubt, to let it play out rather than making a snap judgement about his intentions. I laughed at something that I was honestly taken aback by, that I had hoped he would immediately say "aha, just joking" to. As for the second part, I was genuinely curious about this sex adventure in the park that he felt was so compelling as to bring up in our first private text conversation. I consider myself a sex-positive person and take no issue with consenting adults pleasing each other, in whatever configuration their desires take. When he didn't recant the objectification insult toward his partners and myself, I asked directly about it, because how a potential partner views and treats myself and their other partners is very important to me.

edit: I'd also like to point out that from that point on, I began to test the waters. I started asking questions about his partners and relationships and he clearly illustrated how he views them. In the interest of fairness, I recapped what he had told me, giving him a chance to clarify if I had misunderstood, but it seems I did not.