Update: On Monday, FIFA said "puto" is not a slur is shouted at the World Cup.
Original story:
FIFA, the governing body overseeing the World Cup, is investigating homophobic chants yelled by fans of Brazil and Mexico during their game Tuesday, and the national teams face discipline.

We wrote yesterday about the use of "puto" by Mexican fans at both World Cup games — against Cameroon and Brazil, and the fact they could be heard on TV broadcasts. The slur, which translates into "fag" or "man-whore" or "coward," is chanted during an opposing team's goal kick.
On Tuesday, Brazilian fans stole the chant and used it against Mexican players. FARE, the anti-discrimination group monitoring abusive fan behavior at the event, reported the chants to FIFA, the London Telegraph reports. Croatia and Russia fans were also reported for their fans unfurling neo-Nazi banners.

Piara Powar, executive director of FARE and a member of FIFA's anti-racism task force, told The Telegraph: "It seems that some fans of some countries will take their hatred halfway around the world. These images need to be acted on urgently. The levels of homophobic abuse at some matches is also totally unacceptable. There is some rapid education required before it begins to run out of control.

"FIFA has some strong regulations in place and we hope they use them. Zero tolerance is the approach set out. It is what is required here."

Brazil and Mexico could escape with a warning for what would be classed as a first offense under FIFA's disciplinary code but Russia and Croatia may face the threat of points deductions.

FIFA also issued its own statement:

"We can confirm that we have been contacted by FARE. Prior to this, disciplinary proceedings were opened against Mexico for improper conduct of spectators during the match Mexico vs. Cameroon. As the proceedings are ongoing, we are not in a position to comment further. …
"FIFA takes a firm, zero-tolerance stance against any form of discrimination and racism and this is enshrined in the FIFA Statutes in Article 3 which stipulates that: ‘Discrimination of any kind against a Country, private person or group of people on account of race, skin color, ethnic, national or social origin, gender, language, religion, political opinion or any other opinion, wealth, birth or any other status, sexual orientation or any other reason is strictly prohibited and punishable by suspension or expulsion.' "
It's been amazing to see how many people have commented on various websites defending the use of "puto" and claiming its not homophobic. Some point to it as a Mexican tradition, ignoring the fact that its use at games only started in 2003 (I have shirts older than that).
CONAPRED, the Mexican federal body charged with tackling discrimination, roundly condemned the use of "puto" at soccer matches, saying correctly: "Seeking to eliminate this practice is not trying to stifle free expression, but avoid the normalization of sexism, machismo and homophobia, understanding that the full exercise of all freedom has to be done in respect to the rights of third parties, without discrimination."
While FIFA has focused on racism during soccer matches and started to get tough, it has done very little about homophobic slurs. The World Cup is a great place to start and send a message.