It's obviously not "of the devil". It's simply a very bad film. I have no problem declaring it, in my opinion, the worst film I saw in 2015 . . . and I saw Joe Dirt 2 in 2015. Joe Dirt 2 wasn't "of the devil" either, but it was also a very bad film (but a very bad film that at least made me laugh in spots).
According to the critics on Rotten tomatoes, FF scored a 9% and Joe Dirt 2 scored a 0%. According to the audience, 19% of the people who saw FF liked it. 22% who saw Joe Dirt 2 liked it.
So you, as someone who liked FF are in the minority. You're the one in five who liked it. You're not crazy . . . but the people who didn't like it are more normal than you.
If you can find a post by someone who says: "THIS FILM WAS SO BAD IT KILLED MY SISTER", they're probably exaggerating and you can call them out on that exaggeration.
If, however, someone says: "FF is the worst superhero film I've ever seen." That's a perfectly rational and justifiable opinion that isn't unreasonable based on the objective evidence of independent, professional film reviewers who have rated it among the worst superhero films ever made.