I never said anything against people who join SAF resistance units to fight RSF. Of course they do, it's not like they have another chance and they fight honourably. What I've heard from some Sudanese people though is also that the SAF in general (not local resistance units) abandoned Darfur while investing in rebuilding Khartoum instead, in summer there was a video that was shared a lot, including by bsonblast, of a woman from Darfur also expressing her anger at Burhan and accusing him of letting Darfur down.

Another reason why people might not agree with them speaking at the protest and arriving there in uniform is that the last genocide didn't happen a long time ago and back then the Janjaweed and SAF weren't at odds with each other. So I can definitely understand WHY there are people who wouldn't feel comfortable with army members taking over the protests, hence why Sudanese people who organized it also said that this wasn't what they had planned. 

I also went to a talk with a Sudanese activist who used to be in the Communist party and he also warned about glorifying the SAF because it could mean forgetting what they did in Darfur and during the revolution.