If the point here is that the DNC would prefer to have certain candidates triumph over others, I think we can all agree with that.
If the point here is that the DNC is not above trying certain tricks to help make this happen, some of them very underhanded or outright unfair, let’s just say that it wouldn’t surprise me at all.
But when people go further than that, as they did in 2016, and suggest that the DNC was decisive in determining which candidate became the nominee- that’s where I just can’t agree. I think it way overestimates their level of influence- in some ways it’s a similar argument to those who assert that if not for Russia Trump would have lost. In both cases you’re drawing assumptions which just don’t hold up to real scrutiny.