Engineers Motivation after his ship crashes

I still cannot make myself buy into the Engineers motivation directed by Ridley and written by Damon for his actions after his ship crashes. How could he possibly have a grudge for Shaw for the actions of the Prometheus ship? Why would he go mad as hell straight for the survival unit hunting for Shaw? Even if you buy that his intentions were to kill all earthlings on this planet now that his ship is wrecked, why wouldn't he attempt that prior to take off the first time? It seems to me his unwavering motivation to go to Earth and destroy all(as the plot sets up) should have been continued. He could have simply hopped into another Juggernaut and woosh, on his way. David and Shaw made it look awfully damn easy to grab one. Plot Holes, Continuity errors and plain old plot motivation confusion by characters makes it easy to confuse viewers and keep them guessing unless they stop and think that hey, that just doesn't make sense!