What does she think is going to happen, that people are going to flood the tags with porn just because the creators said "draw what you want"? As if they have any power to stop people from drawing porn or any other objectionable material, or indeed if the people drawing porn care if it offends someone. Really, what are the creators going to do? Telling them to stop is just an empty gesture and would change nothing, not to mention they'd jump all over Rebecca Sugar because such a claim would make her a hypocrite.
"Oh no people are going to draw porn of this cartoon!" Rule 34 is older than the internet. It's older than TV.
Pretty much as soon as animated (or even comic) characters were created, people were drawing porn of them. Like it or not, that's how it is, and it will never stop. These kinds of people have literally never given a shit for over a hundred years, why would they start now just because Tumblr throws a fit?