President Trump is giving Kim a way to “save face” if he so desires. Part of negotiating. You are easily insulted.
If I threaten to bomb your house, would you find it an honor to meet me? I seriously doubt it.
Kim has the capability to create massive death and chaos in South Korea, and elsewhere. He could quite easily ignite WW III if things should escalate and spiral out of control. Again, why honor someone clearly evil like this with even the suggestion of giving him respect or credibility?
I think its safe to bet that had Obama said something akin to this Trump probably would have condemned it during the campaign.