Tekka is intentionally rephrasing the question, using the same pattern with the verb "to come". It's a common rhetorical device to change the focus of a conversation. Tekka doesn't care about what Ren has come for -- he thinks it's more important to remind Ren what he used to be.
A similar example:
Bad Guy: Do you know who I am?
Good Guy: I know who you work for.
Here Good Guy changes the focus of the question to imply that Bad Guy's name isn't important -- that he only gets his power and authority from his employer. Good Guy is saying, in effect, that Bad Guy is nobody special -- he would be nothing without his employer to back him up.
Note: This is the opening scene in The Force Awakens, and Tekka's speech (and death) serves mainly to establish Ren's character as a dark Jedi, capable of callous murder, and to foreshadow some later revelation about his origin story. This foreshadowing adds dramatic tension.