Why would Andre Berto or Victor Ortiz be a better challenge? Both would be good fights for Pacquiao, but they aren't objectively any better of opponents than Bradley

Both, Berto and Ortiz, at least have KO power to hurt Pac and are natural welterweights whereas Bradley will have to go up in weight to fight Pacquiao. So, not only is he not known for having a KO punch but he is also going up in weight.
You're letting your hatred for Pacquiao cloud your judgment. You should be excited Pacquiao is facing someone with a real shot here

Not rooting for a guy doesn’t necessarily mean you hate him. I root for Chavez Jr. but that doesn’t mean I blind myself from seeing that regardless of him being young, hungry, undefeated, and with a belt on his shoulder, he just doesn’t belong up there with the top big names just yet. See what I mean?
Sure, both Bradley and Cotto are not what we want for Floyd and Pacquiao but at least Floyd is going up to Cotto’s comfortable weight instead of weight-draining him.