I went ahead and added a NSFW tag...
Seems like both you and the OP in question wanted it, so there it is.
I would strongly advise people against adding it to other people's questions though... It seems reasonable for someone to judge their own question as being "not safe for work" but less reasonable for someone else to do it.
To ignore a tag, do one of the following:
In the tag’s tooltip, click on the star twice (or once, if you have
favoured that tag). On the main page’s sidebar, click on edit next to
Favorite Tags. On /users/preferences, use the respective field in the
What do "favorite tags" and "ignored tags" do?
After further investigation I'm thinking that "NSFW" is probably a bad idea. It's a Meta tag and not a great one.
Perhaps it's better to read the title of a question? In this specific case it was pretty obviously not something you wanted to read more about. You clicked anyway and then engaged with the op in what turned into a mess. I'm not saying that the question was good, by any stretch, but you kind of knew that you were going to have a problem before you opened it...
In these cases, just downvote, flag, and/or vote to close and walk away. If you flat don't want to see it, don't click on it.
Now let's drop it and have waffles or something.