The ban given to former Crawley Town manager John Yems for racist language is "a slap in the face to the victims", says anti-racism charity Kick It Out.
He has been suspended from football-related activity until 1 June, 2024.
"The discriminatory language outlined in the FA independent panel report is simply shocking," Kick It Out said.
While the FA said the case was "extremely serious" and "involved racist bullying over a significant period of time", the disciplinary commission "accepted that Mr Yems is not a conscious racist".
"Nevertheless, Mr Yems' 'banter' undoubtedly came across to the victims and others as offensive, racist and Islamophobic," the report said.
"Mr Yems simply paid no regard to the distress which his misplaced jocularity was causing."
Kick It Out said it will be in touch with the FA to "understand how the panel came to their conclusion".
"Given the seriousness of the incidents detailed, it is very hard to understand how the FA independent panel have concluded that 'Mr Yems is not a conscious racist'," it added.
"We do not share that viewpoint.
"Furthermore, to reduce his prolonged string of offensive, Islamophobic, and racist remarks to simply being 'misplaced jocularity' shows a total lack of understanding about the damage that this language can cause or the power dynamics that exist in the game.
"This decision also sets a dangerous precedent by allowing perpetrators to hide behind a 'banter' defence when intentionally using harmful and discriminatory language."
Yems, 63, admitted one charge and was found guilty of 11 others of racist abuse towards his players. Four further charges against him were found to be unproven by the tribunal, while another relating to racial segregation was dropped.
The FA tribunal's findings included that Yems used a racial slur to describe some of the club's black players, deliberately mis-pronounced a name to make it sound like a racially offensive term, and joked that a Muslim player was a terrorist.
Kick It Out said: "To speak plainly, a 15-month ban given the severity of the 11 proven charges is a slap in the face to the victims of the discriminatory abuse detailed in this report and anyone who has been subject to racism or Islamophobia."
The FA report stated how, in his defence, Yems "categorically denied that he was in any way racist".
Yems had been in charge at Crawley since December 2019, was suspended by the club on 23 April, 2022 and parted company with the League Two side 13 days later, two days after the FA announced it was investigating the allegations against him.
