From what I can tell, the tag already existed in a couple of questions, and @skippy was thinking of ways to help the site by adding the correlation tag wherever it seemed relevant. I appreciate the intention and in particular @skippy's been doing some great things on the site in terms of questions and answers.
However, in this case, we have a tag that I think should never have been created in the first place. Correlation concerns the relationship between two variables. In the limited sense of Pearson's correlation, we are talking about the linear relationship, but in the broader sense it could be almost any bivariate association. Science is all about relationships between variables, and there's not much shared by two questions because they are merely concerned with the relationship between two variables, most of which never mention the word "correlation" explicitly. Many questions on this site are concerned with the relationship between two variables. In fact, there's even a question of what is meant by correlation (is it just for observational studies; what about studies that look at the relationship between variables and how a third affects that relationship). Thus, I agree with Steven. Let's get rid of the "correlation" tag.
If there was any argument for having a correlation tag, it would be for questions that specifically pertain to the "correlation" as a topic. For example: What does a correlation mean? Why use Spearman's versus Pearson's correlation? When can a correlation be interpreted as causal? That said, this site doesn't get many questions like that so I think the statistics tag is probably adequate.
More generally, as our site grows and we have more moderate rep users who have permission to create new tags, we are going to get an explosion of infrequently used tags.
Thus, the bigger question is about how much we want to curate tags.
I guess the main lesson from this experience is if a users wants to edit tags on mass they should probably post a meta-question first to check that the community is okay about this. If a tag needs to be post-hoc applied to 3+ questions, there may often be a reason for why it was never applied in the first place.