Maybe this is a Northeastern thing, but I have no idea why anyone would be bothered by someone interrupting a stupid person as he tells lie after lie. If I were in the same room as someone like Mike Pence, I'd talk over him too.
Like I said earlier, I don't have problems with some crosstalk, but Kaine could be a bit disruptive last night. If he wants to cut off Pence after he's made a point to refute it, fine, but there were times where it seemed like he wouldn't let Pence finish a sentence or a thought, and would often interject with things that were off topic like Trump's taxes. Again, not nearly as bad as Trump was with Clinton, but that's not a 100% get out of jail free card, especially since he was debating someone who wasn't Trump and who has been mostly civil throughout the campaign.