I yield to no one in how much I detest many of these actors' politics, though a Streisand is not quite perfectly abysmal, and a Schwartzenegger is not quite perfectly a muscular free-marketeer. And much of the analysis above is on target. But this quoted comment is a gratuitous insult.
The intelligence involved in creating, producing, and mastering the myriad skills of overseeing a film -- remember, many actors are producers, directors, and writers as well -- is often formidable.
To suggest that (presumably all) actors are "borderline retarded" is to smear an honorable profession, out of dissatisfaction -- again, often justified -- with politicking where they are out of their depth.