9:20 AM PT -- Dave Coulier responded to the John Stamos haters this morning on his Instagram.
"I'm sorry to see a bunch of negative comments as I've just begun my cancer journey.
"It's our friendship (me and John) and this is how we are handling a very tough time. I'm a comedian and humor is what drives me. John knows how to cheer me up and I laughed out loud when he arrived wearing a bald cap - being a true and loving friend and brother."
John Stamos is showing solidarity with his friend and former TV castmate Dave Coulier during his battle with an aggressive cancer, but some people online are taking issue with his method ... calling him insufficiently committed to the cause.
Stamos posted a few pics on Instagram of fellow "Full House" actor Coulier, featuring Stamos wearing a bald cap and shaving Coulier's head, who's going through chemotherapy treatment after his recent cancer diagnosis.
Coulier is battling stage 3 non-Hodgkin lymphoma, an aggressive form of cancer. The pic shows Stamos shaving Coulier's head, and the friends are both smiling ... as Stamos acknowledges he used a little Photoshop magic to make the bald wig blend. A third shot shows Dave's wife, Melissa, and John both kissing Dave's freshly shaved dome.