Is it a good idea to remove the red meat in a catfish fillet? I try to do that with stripers but wasn't sure what the protocol was with catfish.

For me it is. I think this is true for pretty much all fish.

Most of the catfish I keep to eat aren't big enough to have any red meat. But if one does, I remove it.

Yeah if you stick with fish that are only a couple pounds, red meat isn't very prevalent. Once you get to the 5-10lbs range you start getting more and yes, cut it out. 10lbs+ sized fish starts to get a lot of red meat between the "good" meat and the skin. I don't keep anything over 8-10lbs and usually only keep the 1/2 - 3 pounders.

Yes, remove the red blood line from the larger cats, but the small ones don't bother.
On the larger catfish I also remove/cut out that nerve that runs the length of the lateral line usually along with the blood line.

Fillet all of my catfish and remove the red meat if necessary!

If there’s enough of it I suppose yes. I really only keep the big flatheads these days and I don’t recall the last few I’ve cleaned having too much red meat.

red meat comes out of ever catfish I clean, but some don't mind the fishy taste or get us to it.

I grew up eating the red meat no problem here. If I catch a hybrid I take the red from it.

Every catfish is different I've seen two of the same weight Blue or Channel and one will have more Red than the other. So check and see by cutting a small V in the middle of the fillet then you can see just how deep the red goes.