The only way that the SPOe redeem themselves is if they increase immigration levels; people are probably unhappy with the centre-left because there hasn't been enough immigration.
You're partly right. The solution to the "problem" of immigration is to draw in more immigrants and naturalize them, so as to drown out the racist vote. This strategy is already starting to pay off in the US. I wish Europe was smart enough to follow suit...Your suggestion sounds like Soviet-style politics where population transfers were used to combat "unreliable" ethnicities.