Does the mitzvah of loving other Jews(Vayikra 19:18) apply to the Erev Rav?
Yes. It applies to all jews. The Shita mikubetzes kesubos 37b brings the Rama that says viahavta lereiacha camocha applies even to a rasha. The proof he brings is that we apply the pasuk to someone whose chayiv misa about to get killed. Rav Elchanan Wasserman also brings this proof.
Even though the gemara in pesachim implies you have a mitzva to hate a rasha. There could be 2 dinim in the mitzva 1. to love him. 2 to treat him well. Maybe you have to hate him but treat him well...
So if you hold eirev rav were reshaim then at least this din of loving your fellow would apply, that you have to treat him like you want to be treated. Im not saying they were considered reshaim. But if they would be.