The person that Greta was sending hearts to is an 18 year old female I believe. Who chose to join many others to prevent the screening of this documentary out of fear and outrage from what I can see.
I have seen it and I don't think it is controversial but uses plain language that some people would consider unsafe in their heightened sense of being victimised by misgendering.
So, yes. I imagine that there will be 'teenagers' being 'bashed' (figuratively, in the emotionally manipulative usage of the word rather than 'literally' - because no violence should be happening at all) in these threads about this protest and other protests where these extreme activists are protesting, and some even attacking, feminist rallies of any kind.