When the Nevada Democratic Party says your supporters have a penchant for violence, at some point you have to say enough is enough and speak up against that.
I have no problem with them making a statment about the behavior of the Democratic Party during the nomination process. If I got accused of stealing someones phone I don't think part of my protestation of innocence would be that someone stole my bike a month ago. It's a nonsensical thing to insert into the statement. It makes it a statement of victemhood, which I suppose plays well these days but which I find as annoying as a politician telling me that they love their spouse. The Sanders campaign needs to harshly expose every dirty trick the DNC plays against his campaign. If he can make the DNC lose credibility, he stands a better chance at avoiding future shenanigans.
The Sanders campaign has been a victim this entire time. I hadn't heard a single thing about this kind of violence directed at them in Nevada prior to today, nor do I expect I would have if it weren't for today's public release. While I agree with you on needing to go against the DNC as harshly as possible, I'm completely okay with them including that statement even if it doesn't completely mesh with the rest of the points they're making. If only because it raises awareness.
While perhaps not as relevant as the other points made in this release, it does put in perspective the largely verbal "violence" Sanders' campaign has been accused of. It may also intend to portray the event as a targeted attack against the campaign, but I agree it loses its effectiveness without an existing link to Clinton or her campaign. How would one expose the dirty tricks without signaling some degree of victimhood? And might Bernie have some threshold of damage to the DNC's reputation he isn't willing to cross?