Is it ever ok to say mean or sarcastic comments to someone?

In general I think of myself as a good person and rarely do I say anything mean or negative to other people, but every once in a while I will catch myself making a negative comment on the internet. Often after it is posted, I will think about it and wonder if I did the wrong thing by posting something that might hurt the feelings of another person. So I started thinking, is it ever ok to say mean or sarcastic comments to someone?

Although I don't necessarily think it is a good idea to do this, I think there are certain situations where it may be acceptable. For example if someone says or does something stupid, I think it is fair to call them out on what they did or said that was wrong. You might be able to do this in a nice way, but I find often a stupid action is best responded to with a sarcastic reaction. I don't even like sarcasm but I find in these situations it can be appropriate as a response.

The event that inspired this topic was seeing a video on Reddit that was obviously fake and yet it was getting a lot of support from people who apparently did not realize this. Not only that, then you have people who see the support it is getting and then they copy it and repost it as if it is their own.

Both of these things are looked down upon in my opinion. One, staging a video and uploading it as if it is something that really happened in attempt to trick people into thinking you spontaneously captured something interesting on video when you did not. Two, copying and reposting that content as if it is your own in attempt to get support of your own for something you did not create.

So when I see examples like this of people doing things I would consider wrong, I feel like they need to be called out on it. So I might make a comment about how it is obviously fake, or might link to the original post and make some sarcastic comment about how it has been posted already. These kinds of comments might seem mean or negative but I feel like if someone is going to do stupid things, they need to be ready to accept the consequences of their actions, and in this case it is going to be negative comments.

What are your thoughts on the issue?