no offence

a phrase used to imply you are about to offend someone

"No offence but your dress looks shit."

Offence Plea

To claim you are offended by something someone else says, no matter how insignificant or small it is, in order to play the martyr and gain the support of others even if you are in the wrong.
A tactic uses by people who are losing an argument to try to be the victim and gain support of others.

Don't try to use an offence plea here buddy!
A simple debate went wrong when the guy used an offence plea to gain support.