My apologies, but I really don't think it's your place to make a call on something like this. You have no basis as to what he actually felt like and have nothing to back up any reason why MLP would make depression worse in any way shape or form. My Little Pony is a very upbeat and happy show and many people can connect with it on a deeper level. Many of my brony friends have said that ponies contributed to their getting over depression, myself included.
Please don't just say things like that, it's negative, unnecessary and just downright rude.