Look at these angry children.
tbh the way I see it is that Lance not only COVERS his feelings for Keith with rivalry, but also mixes them with it. I think that he hasn't realized that he's bi yet, and although he probably thinks about Keith a lot and admires him, he's mixed all of it with rivalry and hate back at the Garrison. I have a feeling that one day he'll be just like... he's gonna realize his real feelings for Keith all at once (maybe after another klance moment?) and that's also when bi Lance arc starts