The correct response is the same as for any other scientific result: Was the experiment designed correctly? Was it executed correctly? And (most importantly) has it been reproduced by other investigators?
Thus the effects are not really tiny. The direct effect of a genetic variant may be tiny, but it is associated with many genetic variants with similar effects.
This is most obvious in the Ashkenazi population, which has been so strongly selected for intelligence that it now suffers from numerous recessive problems. If you have a trait found in that population, the chances are good that you have other traits found in that population.