Melanie Eversley

USA TODAY

NEW YORK -- A bus spreading a message against transgender culture was vandalized near United Nations headquarters early Thursday evening while it was parked, according to the head of one of the three groups organizing the bus tour.

The "Free Speech Bus," as it is called by organizers, was parked near the UN for a scheduled event when two people approached, scratched it with a key, cracked windows with a hammer, and spray painted slogans such as "Trans Liberation," Brian Brown, president of the Washington-based National Organization for Marriage, told USA TODAY.

The people on board the bus traveling between points in New York, Connecticut, Washington and Boston were inside the UN for an event, but the driver was with the vehicle, Brown said. The driver tried to protect the bus and was tackled but not hurt by one of the vandals, Brown said.

Brown's organization put together the bus tour along the East Coast along with Citizen Go, a social activism group that works through online petitions, and the International Organization for the Family, a Washington-based group that promotes "the natural family."

"Boys are boys and girls are girls - it's very simple," Brown said of the bus tour's purpose and message. "We don't want men in girl's restrooms. We don't want schools and our law attempting to say that people are bigoted simply because they understand that there's a difference between male and female."

Of the alleged vandalism, Brown said, "If they thought that would silence us, they were totally wrong."

The New York City Police Department said it took a report on the alleged vandalism and that it is being investigated as an incident of criminal mischief.

The bus received a tumultuous reception in New York, a city known for its open support for LGBT rights and for its number of organizations supporting the LGBT community. Brown said as the bus made its way through New York's streets, it was greeted with the thumbs up from some people, and "some other hand signals" from others.

Pro-LGBT organizations condemned the intention of the bus, calling it the "Hate Bus."

"Free speech is a constitutional right, but language has consequences that must be considered," Jessica Stern, executive director of OutRight Action International, a pro-LGBT rights organization based in New York, said in a statement e-mailed to USA TODAY.

"Trans youth already have an extremely high risk for violence, discrimination and suicide. Broadcasting a message that erases and denies the reality that transgender and intersex children and youth exist (sic) is irresponsible, factually misleading, disrespectful and dangerous," Stern said.

Gillian Kane, senior policy adviser at Ipas, an international women's health and reproductive rights organization, is calling on Mayor Bill de Blasio and the New York City Council to denounce the message of the bus.

Media representatives at City Hall did not immediately respond to an e-mail sent Thursday evening requesting comment.

The vandalism incident will delay the bus' tour by about a day while it is repaired, Brown said. The tour will head to Yale University in New Haven, Conn., Boston, and then return to Washington next week, he said.