Maybe they were playing in Open because of the enjoyment of playing in a cooperative manner with other people.
Clearly, we're unaware as to the circumstances. e.g. were they the bad guys, wanted already, shooting up innocent other CMDRs. Or were they simply haulers, jumped by a player who fancied showing them who's boss.
There's a 50+ page thread about PvP vs PVE in open, maybe you should join that. The key thing being said in there was that Open is OK as a place to kick other players. Can't say I agree.
My personal view is that right now, the rules allow a LOT of things that shouldn't be the case in open, including combat logging, and a LOT of undue piracy and wanton destruction.
The answer is NOT the players. It's the LAWS that should be applied at various levels in human space. Right now, they're simply inappropriate for a thriving economy, as they have too little penalty for the bad guys.
Solve the laws, you'll solve how the players play.