Obama was referring to working-class voters in old industrial towns decimated by job losses when he said:

"They get bitter, they cling to guns or religion or antipathy to people who aren't like them or anti-immigrant sentiment or anti-trade sentiment as a way to explain their frustrations."

He never said or implied they were stupid, just putting a reason behind the way they feel. But it's understandable why some people would be offended, especially when misquoted out of context.

Clinton said during the 2016 election:

“You know, to just be grossly generalistic, you could put half of Trump’s supporters into what I call the basket of deplorables. Right? The racist, sexist, homophobic, xenophobic, Islamaphobic—you name it. And unfortunately there are people like that. And he has lifted them up.”

She then said the other half of Trump’s supporters “feel that the government has let them down” and are “desperate for change.”

What she said is basically true, but certainly came off as elitist and the Trump campaign certainly ran with it.

But I agree with another commenter that pretty much anytime you sound like you’ve read some books past 8th grade some conservatives will call you condescending. It’s all part of the language that politicians have been weaponizing to take advantage of the ever-growing division between political extremes.