It's pretty much because they feel like Disney is forcing LGBT+ characters into their face with LeFou and sneaking sexual innuendos into their films (Example: When Simba hits the ground after an exhaustive night, the dust flies off and spells "Sex" or something like that). Disney has always been in the spotlight of controversy with them being sued by the author of Bambi during WWII, I heard the case is still ongoing and Donald Duck having a nightmare where he was a soldier in WWII Germany.
Anyways, back on topic, they just think that Disney is forcing their kids to question their sexuality at an early age with LeFou and Good Luck Charlie. They could act a lot more mature about it.
As Master Spockanort mentioned earlier, LeFou might make a strawman out of the LGBT+ because of his status within the story, he's the villain's comic relief henchman. Therefore, LeFou will probably get it into people's heads that all LGBT+ characters are like him since there isn't much to any that are known to be the hero or on the hero's side.
I would say that Lumiere and Cogsworth's relationship should be expanded upon. Not necessarily re-writing the characters, but possibly have Lumiere and Cogsworth having feelings for each other. Cogsworth could be using his prudish attitude as front towards Lumiere disregarding the master's orders and also he is also ditching him for other women.
The whole controversy thing will pass. Frozen was also accused of promoting LGBT+ issues because Elsa was saved by her sister, instead of living happily ever after with the guy. These people pretty much accuse Elsa and Anna of being in a lesbian relationship, despite the two being sisters. Of course, these same people that are starting this controversy might also be accusing Belle and Beast of promoting bestiality since Beast is technically not human at this point and Belle is human.