Biological Exuberance. Even though homosexuality is the leitmotif of this text, there are instances in which sexual activity between cubs and between adult and cub are discussed.
217-A. This law also applies to other situations in which consent isn't legally valid. It also doesn't set a minimum age for the offense. So, in Brazil, if you are 12 and you kiss your 12-year-old girlfriend, you are a rapist. Go figure.
Children, Sexuality and Sexualization. In the chapter "Boy's Love Manga for Girls", Madill shows that, in the UK, a picture can be legally questionable even if one of the subjects in it appears to be a minor. It doesn't have to be a real minor. Madill then goes on to show how this affects the status of legality in some manga works, as well as how the law enforces a specific reading of the work, when art is supposed to be interpreted in several ways. That being said, the fear that people can call art that appears to be cub, despite not being cub, into question is plausible.
Discord's lax policy on furry "cub content" leads to user outcry. Discussion at Kiwifarms. Notice how it gravitates the "it's disgusting" statement, with no discussion on child welfare whatsoever, except for one user who mentioned that Discord is supposed to be more worried about minors building servers dedicated to erotic roleplay.