No one is claiming that intelligence isn't genetic. Certainly not "the left."
The claim is that race as commonly understood and defined (specifically by eugenicists like Watson) has no genetic basis, and therefore claims which follow from that definition such as "Asians have higher IQ" are not scientifically valid, and do not prove the validity of Watson's racial views.
For some reason sparkie just decided to reframe my comment around a claim I didn't make and now here we are litigating a "leftist" strawman.
"Intelligence isn't genetic" is the left's version of creationism.