Sam,
There are negative feelings and positive feelings. (ex: NOT to hate ?? ???? ?? ???? ????? and to love ????? ?? ? ) That the Torah can command us not to have certain feelings is clear.
It’s definitely within human capability to control negative feelings using certain techniques.
Commanding someone to have positive feelings seems to be a chiddush and I believe the question is asked when we are commanded to love Hashem.
The answer is that we really DO love Hashem. The commandment is to peel away the layers and to get in touch with our true feelings.
I do not know what you are referring to with Rabbi Soloveitchik.