Juggernauting

The act of sticking to a topic of conversation regardless of the interest of those around you, or their attempts to change the subject.

Man 1: Hank smoked a bowl the other night and preached about Warhammer 40k for 3 solid hours!

Man 2: Why didn't you just change the subject?

Man 1: We tried. He was juggernauting, there was no stopping him.