It depends what kind of activist we are talking about. If the activist was for human rights, we could possibly consider them as a humanitarian, because the definition for humanitarian is: concerned with or seeking to promote human welfare. This is quite similar to a human rights activist, so I would say yes.
The effects of bullying are very sadenning. Bullying may cause depression, hatred towards others, which can result in you becoming a bully yourself, and, bullying can even cause suicide.
