Democrats denounced the bill, which passed 68-22 in the GOP-run House, classing it with Republican "religious freedom" measures in Tennessee and other states targeting gays, lesbians, bisexual and transgender people.
Rep. Dan Howell, R-Georgetown, is the House sponsor. The Senate already passed a version, but will have to reconsider it because of a House amendment that proponents think will be accepted.
The debate laid bare philosophical differences as tensions between majority Republicans and most of the House's minority Democrats.
Howell and Republicans argued House Bill 1840 is necessary because of American Counseling Association standards adopted in 2014 that apply in Tennessee.
The ACA standards say therapists may not automatically deny service to someone solely because of their personal beliefs. The rule came after the 6th U.S. Circuit Court of Appeals ruled that a Michigan college student couldn't be kicked out of school for asking a gay client to be referred to someone else.
Howell said the ACA "overstepped their authority and elevated their code above the First Amendment, and that's why we're here today."
He and others said the bill protects professionals' constitutional rights while providing adequate safeguards to ensure proper referrals. He also said therapists previously had been able to refer patients elsewhere when their goals were at odds with the therapist's own religious and personal views.
Rep. Mathew Hill, R-Jonesborough, a religious broadcaster, told colleagues, "We are standing up for everyone's right when we vote for this bill."
Critics claim the bill allows counselors and therapists to avoid serving vulnerable people, such as LGBT teens who come seeking help, and flies in the face of professionals' duty to set their personal views aside and assist people in trouble.
Rep. John Ray Clemmons, D-Nashville, said the bill affects people when they are most vulnerable.
"I would be embarrassed if Gov. Haslam were to sign this, because it sends a clear message to the rest of the country that Tennessee endorses discrimination," said Clemmons, noting no other state has passed such legislation.
The ACA opposes the bill, and the Tennessee Equality Project denounced the House version as "Hate Bill 1840" and the "Counseling Discrimination bill." The gay rights group urged Republican Gov. Bill Haslam to veto it.
Clemmons tried unsuccessfully to amend the bill. One provision would have required therapists to treat bullied children, a specific concern in the LBGT community highlighted by the suicides of two Polk County teens in 2015.
While proponents said the bill wouldn't allow counselors to automatically turn away people who might harm themselves or others, critics said referrals would be problematic in rural areas.
Clemons charged that "one special interest group" from outside Tennessee is pushing efforts in various states to overturn the ACA changes.
"Who are they to dictate the access to health care that the people of Tennessee receive? Who are they to make Tennessee an outlier? We cannot allow one special interest group to come into a state and tamper with the lives of people who are needing help and seeking help," he said.
But House Republicans used their numerical supermajority to limit debate on Clemmons' amendments.
Majority Leader Gerald McCormick, R-Chattanooga, stood and read from a recent column by a conservative columnist, citing her remarks about "modern leftism" and saying it applies "to what we're listening to here."
That included statements in the column that "Progressives accept no limits" and people who disapprove of same-sex marriage "will be ruined," he said.
Retorted Clemmons: "If being on the left means standing up for people who need help and the working men and women who need help, then I'm happy to be on the left. The things in this bill have gone so far to the right."
He later cited Republican bills in various states, such as "religious freedom restoration acts" following last year's U.S. Supreme Court ruling on same-sex marriage.
The House Education and Administration Committee was scheduled Wednesday evening to consider another bill that would require transgender students to use bathrooms that match their sex at birth.
Contact Andy Sher at asher@timesfreepress.com, 615-255-0550 or follow via Twitter at @AndySher1.