Here is a photo seen on Facebook on January 11 on the NewInZurich page with photo credits to Marie.
Here is the same statue in front of the Opera House in Zürich two days later on January 13. Apparently voicing your opinion by poster on statues is verboten here. I see that the chair remains, though.
However, there must have been a demonstration at Bürkliplatz (near the Lake) that we missed. You can see it here.