People will look for anything to criticize in a person. The minute you were in a video and they weren't, they flock to the easiest thing to pick at and get other people to pick at as well.
Probably nobody cared about your weight until one person said something, then everyone thought "oh it's acceptable now let me join in" With the fat-shaming culture of the media, that's an easy thing to get people to rally in on, and it's incredibly cruel and a huge problem with our society.
It comes down to human nature and our need to be part of a group. Even if the group is shitty, they want to be a part of something. And for people who are so small in their hearts, the easiest kind of group to join is the group that's "us vs. them"
It's easier to form a club of people who hate something than it is to form a club of people who love something. Remember that, and don't think it actually has anything to do with you.
It's just hive mentality, and a need to feel accepted even at the expense of others. Those people probably have very low self-esteem, or are just very ill-mannered children.
You do you, let them do them. While it certainly isn' fair and it's not what you deserve, unless it comes down to a situation of actual harassment, it's not personal and you should try your best to look at it through that perspective and go on with your fabulous and interesting life.
Cosplays in Progress:
Haruno Sakura (Shippuden)
Theodora (Oz the Great and Powerful)
C. Viper (Street Fighter)
Twilight Princess/BRAWL Zelda (Green BRAWL ver)
Tharja (Fire Emblem Awakening)