Race has never been an easy topic of conversation in America. But the recent high-profile deaths of black people at the hands of police officers in Ferguson, New York, Cleveland and elsewhere — and the nationwide protests those deaths spurred — have exposed sharp differences about race relations among friends, co-workers, neighbors and even relatives in unexpected and often uncomfortable ways.

Put bluntly, many people say, they feel they are being forced to pick a team.

In interviews here and around the country, both blacks and whites described tense conversations in office cubicles or across dinner tables about the killings and subsequent protests. Many described being surprised to learn, often on social media, about the opinions — and stereotypes — held by family and friends about people of other races. In some cases, those relationships have fractured, in person and online.

Kenny Hargrove, a black man from Brooklyn married to a white woman, said he and his wife confronted one of his in-laws for posting a racially insensitive meme on Facebook around the time Mr. Brown was killed. The relative was so upset that she unfriended them. Now, she is trying to mend fences and has sent a new friend request. But Mr. Hargrove, 36, said he was torn about whether to hit “confirm.”

“If I see one stupid thing from you, it’s over forever,” Mr. Hargrove said.

In fact, the day that a Staten Island grand jury declined to indict a police officer in the chokehold death of Eric Garner, Mr. Hargrove posted this to his Facebook page: “This is for anyone still left on my friends list who’s wondering why black people are so angry right now. If you still don’t get it, if you still can’t see the pattern, if you still think the protests are nothing more than angry thugs who just want free TVs, let me know. I don’t have the energy to connect the dots for you, but I do have just enough left to hit ‘unfriend.’ ”

But Peter Weiss, a white resident of Staten Island, said many black people seem unwilling to consider alternative perspectives on police violence.