The student's response is a classic example of circular reasoning, to put the most charitable interpretation on the matter. It is another example of the church's failure to teach people how to think well. Circular reasoning employed in the service of religious tribalism strengthens bigotry and fuels religious wars, both private and large-scale.
"Jesus is Lord" is the earliest known Christian confession of faith. What we do with it matters. In the early church, the statement was not used as a weapon or to divide. Instead, the confession marked one's personal commitment to try to follow Jesus. Most also regarded it as descriptive of their experience of God through "the risen Christ." It was a declaration of identity and intention. To put it another way, the confession amounted to a person saying: "This is who I am--someone for whom Jesus is the center of my life."
Those who take such an approach usually find themselves walking a road that leads to deepening humility, appreciation for the image of God in all others, and sacrifice for the good of others. The way is narrow, though, and too few walk it.