I recently posted a manip of an image drawn by the artist ScruffyTurtles, but posted on their NSFW twitter account, called DeepBeef. I tagged the image as being drawn by Scruffy, as they already have a few pictures on the hub, but someone changed the tag to DeepBeef. Is this correct? It isn't like they are trying to desperately distance themselves from their nsfw account, as they post also NSFW on their ScruffyTurtles patreon page.

Use both tags i assume? its like if an artist goes by one name on deviant art and another name on twitter or furrafinity.

Unless the artist specifically wants to keep the names separate, pick one and stick with it for consistency's sake. If a tag is already seeing use, that one should probably take precedence. If both names are seeing use, that's the time to introduce a tag alias, to convert all of one to the other.

What you can also do is create an artist page, which allows you to list any aliases and urls of that artist, which can be used to help settle these sort of disputes.

It's likely not obvious from the source link that DeepBeef and ScruffyTurtles are the same person, so the person making the change probably assumed you were making a mistake. I would revert it back to scruffy