Recently audio was released on YouTube of a social studies teacher, Tonya Dixon-Neely, teaching her students that the president has extra-legal standing and that individuals can be arrested for making negative comments about the president. As one student attempted to question this, he was repeatedly shouted down and informed that it was okay to question the presumptive Republican nominee but not the incumbent president and Democratic nominee.
Whereas the president has on multiple occasions spoken out on issues that were not related to the presidency (such as the Trayvon Martin shooting, Rush Limbaugh's comments about Sandra Fluke, and the Henry Gates arrest, to name a few), it would make sense for the president to offer his view on the rights of citizens to criticize a sitting president.