Thomas, who won 100 caps for Wales, came out in December
Castleford Tigers are to appeal against a £40,000 fine imposed after their fans hurled homophobic chants at Crusaders' Gareth Thomas.
Thomas, who revealed he was gay in December, was abused during the game.
A Rugby Football League tribunal criticised the club for failing to take steps to stop the chanting and not identifying the perpetrators.
But Castleford chief executive Richard Wright said the club was not homophobic and the fine was "disproportionate".
Wright said: "I'd like to reiterate that Castleford Tigers is not a homophobic club. We are not appealing against the need to rid the sport of homophobic chanting; we firmly support the RFL's Respect Policy and carry out projects in the community delivering equality and diversity values.
"The club is one of the most robust in Super League at promoting an inclusive environment for all sections of the community and we pride ourselves on this fact. I cannot stress it more that we do not condone homophobic chanting in any situation.
"We are however appealing against the disproportion of the fine compared with the charges put forward."
Castleford's lawyer, Rod Findlay, said: "Just as the chanting itself was wrong, this decision is also inappropriate and a £40,000 fine is wholly disproportionate to the events.
"The DVD confirms that this was three faint, short bursts of chanting each of five seconds duration, over a period of four minutes. Two of the chants were drowned out by PA announcements and the third stopped very shortly after commencing as there was no support for it.
"This combined total of 15 seconds of chanting late in the game from a small section of the crowd prompted only one complaint to the RFL after the match and no-one complained on the day.
"Crucially the chanting was not included in the Match Commissioner's report, despite the fact that the RFL pay the Match Commissioner to attend the game to check on any misconduct and specifically abusive chanting.
"The Match Commissioner confirmed he did not hear anything on the day, and was unaware of any chanting until seeing the media later the following week."