Actually, from his point of view, the word retard as applied to his opponents the GOP is exactly correct. The dictionary definition is”to make slow; delay the development or progress of (an action, process, etc.); hinder or impede.” He and O are very upset that their plans for reforming the country on socialist terms are being “hindered” by the GOP and the right.
No, not GOPers! He called liberal activists “f___ing retards.”