you can generally buff out scratches with a buffing compound; popular choices include brasso and mild toothpastes.
scratches on the bottom of a disc are generally not serious damage, because that is not where the data on a disc is. instead, the data is located not too far under whatever printed label on the front there may be; scratches there tend to be quite fatal.
so it's almost a good thing that people have such a fixation on the "shiny side", because that's also the big physical protection of a disc. many scratches on the bottom can generally be buffed out provided they aren't so deep as to have actually hit the top.