I would say Dean did what he had to do after Sam was a cold brutal MF to Benny and HIM. Sam sicced an unstable hunter on Benny who then got the wrong end of the stick completely with regards to who was doing the killing. Sam refused to listen to Dean. Sam allowed Dean to be knocked unconscious and chained up so that HE could go kill someone who was not at all guilty of what he was being accused of.
Dean was left with very little choice given Sam would not listen to him and was on this crusade to find any excuse he could to kill Benny, he had to do something to try and save Benny's life. I'd say that is more on Sam's being entirely unreasonable for no good reason other than his own pettiness and jealousy and looking to somehow even the score for killer Kitsune Amy over a year later. Dean wouldn't have had to take such an extreme action if Sam hadn't gone to such extremes and that wasn't putting someone else's life in danger. I doubt he thought Sam would just abandon another hunter in the middle of a literally active(not just research active but the actually physically dangerous part of the) hunt as opposed to calling it off or saying he needs his help to go with him or something of that sort and they could deal with this vampire later.
I didn't think anything in Blood Brothers was cold. Dean decided they could use some help, so he called Sam, in fact he was trying to get Sam off the phone quickly, held the phone to his chest to try and keep down the noise and texted him his information and asked Sam to stop talking but Sam kept talking so Dean used the opportunity it provided. I don't think that's cold just" hey he won't keep it down after I've asked him to, might as well use to my advantage instead of letting it get me killed."