Jesus said love everyone. Treat them kindly too. You fill in the rest.
There is also that little thing about forgiving others.
So - I suppose if you hate BYU or BYU fans, and are unwilling to forgive them their faults...then in essense you are sinning. Or at least not doing what is required of you as a member of the LDS church.
And I fully recognize that there are BYU fans and players who also have this same fault and need to work on it.