Should lipid lowering therapy be started in patients with isolated elevation in lipoprotein (a) and minimal cardiovascular risk?  

At the current time the answer would be "no" for someone with minimal CVD risk. There are not any currently available therapies for effectively lowering Lp(a) nor randomized trials demonstrating clinical efficacy, though this could change in the near future.

I agree with Professor @Kraemer (hi!) with two exceptions. First, there IS in fact one currently available therapy, lipoprotein apheresis (LA) which dramatically lowers Lp(a) levels (by 65-85% acutely and by ~30-60% time-averaged) and even more dramatically reduces CVD risk (by 70-95%! NOT a typo)....