NEW YORK - As a leading defender of abortion rights and comprehensive sex education, Planned Parenthood deals daily with some of America's most contentious issues, and is well accustomed to receiving verbal threats.

Some of the organization's supporters say Friday's deadly shooting at its clinic in Colorado Springs shows that the vitriolic rhetoric could be inspiring actual violence.

Killed in Friday's attack were a police officer, Garrett Swasey, a father of two; and two civilians, who were accompanying separate friends to the clinic. The civilians have been identified as Jennifer Markovsky, 36, a mother of two, and Ke'Arre Stewart, 29, an Iraq War veteran and father of two.

"It is time to stop the demonizing and witch hunts against Planned Parenthood, its staff, and patients," said Sen. Barbara Boxer (D., Calif.).

But critics show no signs of backing away from a multipronged offensive against Planned Parenthood, keeping protests and a congressional investigation on their agenda for the coming year.

Robert Lewis Dear, the man arrested in the attack, uttered the phrase "no more baby parts," a law enforcement official said.

Authorities have not elaborated on the gunman's possible motives, but Planned Parenthood said witnesses described him as an abortion opponent. The "body parts" phrase echoed rhetoric that surfaced last summer, when antiabortion activists began releasing undercover videos they said showed Planned Parenthood personnel negotiating the sale of fetal organs.

The antiabortion group that made the videos, Center for Medical Progress, condemned the "barbaric killing spree in Colorado Springs by a violent madman."

Planned Parenthood said any payments were legally permitted reimbursements for the costs of donating organs to researchers, and has since stopped accepting even that money. Though the videos have inspired multiple investigations in Congress and in several states, none has confirmed any law breaking by Planned Parenthood.

Planned Parenthood has remained in the news since the videos were made public, with most Democratic politicians supporting the organization and many Republican leaders assailing it. Republicans have sought to cut off federal funding for Planned Parenthood, and several GOP-governed states have tried to block Medicaid funding to the organization.

All the Republican presidential candidates say they favor restricting abortion rights. Some were asked about the Colorado Springs shootings on Sunday's talk shows.

Mike Huckabee condemned the attack as a "despicable act of murder" and said "what he did is domestic terrorism," but then equated the killings to the abortions Planned Parenthood provides.

"There's no excuse for killing other people, whether it's happening inside the Planned Parent headquarters; inside their clinics, where many millions of babies die; or whether it's people attacking Planned Parenthood," Huckabee said on CNN's State of the Union.

Such comments are "unconscionable," said Dawn Laguens, executive vice president of Planned Parenthood.