So let me get this straight: The timeline where some guy FROM THE FUTURE traveled back in time to kill Barry's mother is the "correct" timeline while the timeline where Barry's parents live a normal life is the fucked-up one? Also, Cisco had no justification for resenting Barry's refusal to prevent Dante's death. Barry's mother's death was due to timeline interference by Reverse Flash while Dante's car crash was a normal, albeit unfortunate, occurrence. Barry saving his mother should be seen as an attempt to restore a broken timeline rather than a selfish desire to protect a loved one. I would hope that Cisco would be able to see that logic through his grief.