That's not as surprising as you may think. "Truth is not a complete defense against libel".

Imagine I contacted someones workplace and business partners and told them about a drug conviction that occurred 22 years ago. Or if I took a statement you make after a some drinks in the pub and stuck a print out on poles all around your business.

There are cases where suing someone for libel even if what they say is true doesn't seem demonstrably wrong.