1 Reason Why Evil Morty Isn't Rick's Original Morty (And 5 Why He Is)
3. Evil Morty's Specific Discussion With Rick
When we're first introduced to Evil Morty in the episode Close Rick-counters of the Rick Kind, we're led to believe that he is following his Rick. Of course, this is subsequently shown to be untrue, as that Rick is a robot which is being controlled by the eyepatch Morty (later Evil Morty).
After our Rick and Morty are captured by Evil Rick and Evil Morty, they are separated and Rick is tied down on a table with a device hooked up to him that will read his memories. We find out a great many things in this scene (some of which will feature later), however when viewed with the knowledge that this was actually Evil Morty having a discussion with Rick, the game changes - specifically the line Evil Rick says about Ricks not caring about Mortys.
This line gives an indication as to why Rick C137 is the target of Evil Morty in the episode. Perhaps Evil Morty has been betrayed by Rick at some point in the past and is using the robot Evil Rick to get some answers out of him.
It becomes clear that Evil Morty's plan was to kill Rick after taking his memories out. Though, more intriguingly Evil Morty has no real feeling toward Morty C137 when he meets him, other than to just put him in a cell with the other captured Morty's. This indicates that his beef is with just Rick C137, as opposed to Morty C137 too.