The movie was incredible until the ending. Spoiler alert.
Sure it wasn't exactly right for Evan to lie about being friends with Connor but the man didn't really have a choice. Connor's mom pressured Evan to say something positive about him even though there wasn't any. Evan being shy and having serious anxiety, only multiples the stress. Instead of being hated by the family he lied to, they should have realized that Evan didn't wish any harm.
Here is what I feel what I think that could help the movie. First, if there was scene where Evan eventually snaps and yells to the family about how stressed out he was at the time when he was pressured by Connor's mom.
Second, after Evan tells the family how he felt, they realize how wrong they were to blame him and then forgive him.