Protesters blocked the entrance to a Mexican art gallery on Tuesday over a painting showing revolutionary hero Emiliano Zapata striking an unconventional pose.
The painting, which is on show in Mexico City, shows Zapata, naked on a horse, in high heels and a pink hat.
Zapata's grandson Jorge Zapata González called for the painting to be removed.
Scuffles broke out between the protesters and counter-demonstrators defending sexual diversity.
"We are not going to allow this," Mr Zapata González told the Associated Press.
"For us as relatives, this denigrates the figure of our general, depicting him as gay," he said, adding that the family would sue if the art is not removed.
The protesters, mostly farmers who support Zapata, said the painting "denigrates" the image of their hero.
Some shouted homophobic slurs, which angered members of the LGBT community holding the counter-demonstration.
The 2014 work by Fabián Cháirez is part of a Zapata exhibit at the capital's prestigious Fine Arts Palace. It has already been on display elsewhere.
Luis Vargas, curator of the exhibit, said the painting was simply an artistic representation that sparks debates about issues in Mexican society including homosexuality.
Zapata was a leader in the Mexican revolution before being assassinated in 1919 at the age of 39. He remains a hero in the eyes of many Mexican nationalists.