Because you turned a completely innocuous discussion about nude beaches into an unhinged rant about sexualizing children. Nudity does not inherently mean sexual.
A short comment like “yeah I don’t know how I’d feel about children at a nude beach” would have been fine, but the extent to which you’re talking about it comes off as creepy and projecting.
I started using eM Client for mail on Windows, and its calendar integration is pretty decent too. It’s paid software, but you only have to pay once.