If the Democratic party rigs the primary for a garbage candidate, then I really hope Bernie runs as an independent. He'd be the stronger candidate, and so if Trump got re-elected, it would have been the Democratic party and not him who was the spoiler.
Define rigged. If the superdelegates overturn his delegate/popular vote lead, then yeah I'd agree with you it would be justified. If you mean irrelevant DNC operatives privately sending snarky emails about him, then yeah...no.
The DKIM verified Wikileaks e-mails showed that the DNC was very biased in favor of Hillary. Including things such as having Donna Brazile feed Hillary debate questions ahead of time. You can find plenty of information online about the Wikileaks emails such as this.
http://observer.com/2016/07/wikileaks-proves-primary-was-rigged-dnc-undermined-democracy/
You mean telling the Clinton campaign they would be getting a question about the drinking water in Flint while debating in Flint at the height of the Flint scandal? Yeah, that was really putting the finger on the scale for Clinton. /s