[02/XX] ...the part that could be art. However, merely intending a text as irony fails to do that. It doesn't present the meaning in a subtle way, because the subtlety is not in the work itself; rather, the artist hopes that it will come up in the viewer's minds only.
As for the effectiveness, it seems that many of the public did not notice the irony and mistook the quotation from the regime for support — and they responded by painting over it with non-ironic condemnation of the regime...