Not long after launching LoL, Pendragon replaced the whole site, including: hero page descriptions, various Dota related web-tools, forum, etc., with a JPEG link thanking the Dota community for all the fish and pointing everyone to the LoL site.
He released the forum database available 5 years later, I think, when it didn't matter anymore.
The LoL advertising during the early period was extremely Dota-hostile. Dota 1 had its flaws, but they were basically pissing all over it.
Tournaments where LoL was played were paid to ban any kind of LoL competitors (generally aimed directly at Dota 2).
Etc., etc.