He is British. "With all due respect" means no respect is due. I don't think it's possible to show less respect while appearing polite. In other words, them's fighting words.

http://todayilearned.co.uk/2012/12/04/what-the-british-say-v...

This is perfectly fine if the amount of respect due is sufficiently low.

Given the answers that cloudflare is giving I's say it's quickly approaching zero.

Ha! Excellent point!