Agree with Greenwyvern - you show where Jack's coming from (building up on the show's clear portrayal of Jack's identification with john) and show on top of that how, as he can't actually make himself admit to the team why he's feeling this way, he takes all his feelings out on the "safe" target: Ianto. After all, he'd never treat Tosh that way (he always seems to regard Tosh as the fragile one in that sense), he knows damn well that Owen and Gwen would bite back and he assumes, if he thinks about it all, that Ianto will just forgive and forget.

oh God how nasty is he going to get when he brings John's body back? After all, it's Ianto's car, and it takes Ianto a while to realise the keys are missing....