Rev. Jesse Jackson speaks to media outside federal court, Wednesday, Aug. 14, 2013, in Washington, after his son, former Illinois Rep. Jesse Jackson Jr., was sentenced to two and a half years in prison after pleading guilty to scheming to spend $750,000 in campaign funds on TV's, restaurant dinners, an expensive watch and other costly personal items. His wife Sandra Jackson received a sentence of one year. (AP Photo/Carolyn Kaster) The Rev. Jesse Jackson on Aug. 14, 2013 (Carolyn Kaster/AP)

The Rev. Jesse Jackson said in a tweet Wednesday that the killing of an Australian baseball player, allegedly by three Oklahoma teenagers who were bored, is "senseless violence" and should be "frowned upon."

Conservatives and others on social media immediately criticized the remark as tepid and insincere — especially in light of Jackson's and other black leaders' strong reactions to the killing of Trayvon Martin, a young black man, by neighborhood watch volunteer George Zimmerman last year.

The teens who stand accused of the crime include two who appear to be African American.

Even before Jackson's tweet, conservative media criticized civil rights leaders for not offering a similar response to Lane's murder as Martin's.

One of the three teenagers involved said they were bored and decided to kill somebody, according to police.

Critics of Jackson's remark began tweeting with the hashtag #frownedupon, noting other far-less-severe things that are "frowned upon."

A sampling of the response to Jackson's tweet: