I moved to Spain from the UK a few years ago now, and while not really 100% behind this law, I think there is a point to it.
Spain only left a dictatorship just over 30 years ago now, and we have to respect how far the Country has come in that short space of time. It's a much more open and freer society now (obviously!). However in 30 short years, you sort of can't expect large cultural changes immediately.
This law, as it sinks into people's awareness, might slowly work to create a better respect for animal care and husbandry. You can't expect bull fighting to stop over night as it so deeply ingrained into social fabric. However, I believe the new law will raise awareness and lead to a growing demand for bull fighting to stop eventually.
Remember how long Fox Hunting took to remove in the UK. Still there are illegal hunts and on going political rows about the 'sport'. Perhaps (and I might be giving them more respect than they are due) Zapatero's Gvt are trying to shift culture gently. I bear in mind though that even though we are in a credit crunch, and here we are feeling the pinch badly too, we still get nightly bin collections, we have a good Police force, and our hospitals (well last time I was in one our local one) are excellent.
So 300 years to ban fox hunting, 30 years free of a dictatorship to start trying to improve animal husbandry. I think it's a start.