Why? The only thing wrong is he dated someone who wasn't honest about his existing relationship status. Hell we don't even know if the wife is unaware. She might be okay with the husband having a "play" date but doesn't want him developing a long term or recurring thing (this would be some insecurity on her part) with someone. Nothing about this suggests that people who are bi or pansexual are less honest, trustworthy, or worth your time. So if that's your intention, and that IS the insinuation you're making whether you intended it or not, then you're waaaaay off base and very rude.

What exactly were you expecting from Grindr?