Besides Loras is there any other evidence that Renly looked down on Brienne?
I don’t think and don’t remember that Renly ever treated Brienne with open contempt; he gave her the public honor of a rainbow cloak the moment she asked for it without sneering or even batting an eyelid at her being a woman, he let her carry his standard and help him don his armor; in other words, on the surface, he was courteous and respectful of her dignity and role as a member of his kingsguard. So I’ll credit him for that. This is also why it’s hard to find objective evidence of Renly looking down on her, since we don’t have his pov.
We have however Catelyn’s impression of the Brienne/Renly dynamic, and it’s not positive:
The way she looked at the king - looked down at him, she was a good hand higher, though Renly was near as tall as his brother had been - was painful to see.
Brienne dropped to her knees. “If I must part from Your Grace, grant me the honor of arming you for battle.” Catelyn heard someone snigger behind her. She loves him, poor thing, she thought sadly. She’d play his squire just to touch him, and never care how great a fool they think her.
Brienne was on her feet as well. “Your Grace, give me but a moment to don my mail. You should not be without protection.” King Renly smiled. “If I am not safe in the heart of Lord Caswell’s castle, with my own host around me, one sword will make no matter… not even your sword, Brienne. Sit and eat. If I have need of you, I’ll send for you.” His words seemed to strike the girl harder than any blow she had taken that afternoon. “As you will, Your Grace.” Brienne sat, eyes downcast.