xkcd #3122: Bad Map Projection: Interrupted Spheres
Title text:
During the most recent glacial maximum, it’s believed that land bridges extended from the surfaces and connected several of the spheres together.
Transcript:
Transcript will show once it’s been added to explainxkcd.com
Source: https://xkcd.com/3122/
The tone was condescending yes.
The tone was humorous. You took it as condescending.
Communication is a two way street. If what you meant to convey as humorous did not land as such, but instead as condescending, maybe try reflecting why and how you can improve your communication in the future.