Not fraud if you have the legal right to do what was done.
There is no legal right to rig the election, jackass.
There is no legal requirement to even have a primary election, and any practices used are strictly determined by the DNC and can change at any time. Half way through the primary, they could have decided that the final candidate would be determined by a dance competition, and they would be perfectly legal to do that. They could have chosen someone who wasn't even on the primary ballot for their candidate, and they would be perfectly legal to do that. You're whining about something that didn't even concern your party, and that you know nothing about. Why are you doing that?
For the presidential election, there are very specific rules, and there is an investigation happening right now to see if those rules were broken.