I have no idea about what would have happened if it was a Labour MP, or UKIP, nor do I really care. The issue to me seems to be that there are a lot of MPs and MP supporters shouting about abuse, much of which would one have been ignored, and when more serious issues such as death threats are devalued by being made up, then we are simply seeing a bit of band wagon jumping.
Calling someone a warmonger or responsible for the deaths of children for voting for bombing Syria, is incorrect and OTT, but isn't a threat or bullying. Social media means that we all get to see what was once said in meetings or in the pub, along with all the various protests saying exactly the same thing that were just taken as part of the process.
Even then there were lots of death threats, though most were ignored, as mere loons.
Having gone through the joy of the Independence referendum, I have seen the drive to create a narrative that one side is full of organised bullies, whereas 'our' side may occasionally get out of hand but they are rogue elements and anyway the other side started it. It's a specific and deliberate attempt to create an 'other' and deny the equivalency of any such death threats. If you add into that making shit up, then this is simply propaganda and is an insult to any MP who receives genuine threats.
The original email is hardly shocking and once would have been the subject of joking around the committee table on the basis that it's actually not badly written, has a speck of inventiveness and 'well they would say that'