Jesus was referring to loving others, not "being" perfect. If we live by the Spirit, it most definitely something that can be done.
I don't think this is the case with that passage but I will let them take that up.
Regardless it does not change the fact that NO MAN can keep the commandments- yet God commands all men to do so.
Why? Paul said, "I had not known sin but by the law" and "the law is a schoolmaster bringing us to Christ" and "that sin might appear exceeding sinful".
God commands men to do what they cannot do. That is plain. It is abundantly clear. To say that God would NOT do that is clearly wrong and against the clear teaching of Scripture.
God absolutely does command men to do what they cannot do.
That they cannot do it is tremendously clear as well. Paul said, "The carnal mind is at enmity with God and is not subject unto the law of God NEITHER CAN IT BE."
The carnal man CANNOT be subject to it but God commands him to any way.
Repentance is also a command. "God commandeth all men everywhere to repent."
To say that God would not command men to repent if they cannot requires support. You cannot offer any support because it is not there.
There is absolutely NO reason to say that God would not command men to repent who cannot, especially when it is abundantly clear that he does that with the commandments.