What is the ruling on saying "O cheaters, don't look at the keyboard" for a game in a forum?

It is not permissible to describe a Muslim with an unbecoming attribute. Muslims should purify their tongues from anything that might cause the devil to sow discord among them, even if it is in jest. Allah Almighty says: "And tell My servants to say that which is best. Indeed, Satan endeavors to sow discord among them. Indeed, Satan is ever to mankind a clear enemy." And in the noble Prophetic Hadith: "And is there anything that casts people into the Hellfire on their faces—or he said on their noses—except the harvest of their tongues?"