Is there any danger of giving harsh opinions on the internet?

I don't think you can get told off for it, as long as you don't swear or threaten anybody. It also depends on if the person who you said that to is offended or feels like that was a mean thing to say, as long as you know it was harsh its good, and if the person who you said that to tells you that it wasn't very nice you could always apologise, sometimes all you need to say is sorry. Hope I helped