Curfews imposed in French cities as rebellion against austerity grows nationwide
(breakthroughnews.org)
As I mentioned, cutting defense spending or increasing corporate taxes are also austerity measures. Presumably you're not opposed to those.
Some austerity measures kill people. Those are the ones you're opposed to. That does not mean you are opposed to austerity policies; it means you are opposed to those specific policies.
And regardless of my personal opinion on what "austerity" means, the point stands that a skilled propagandist would want the general public to believe these protesters are irrationally opposed to responsible money management, and calling it a "rebellion against austerity" is an effective way to do that. This is because most people treat "austerity" and "fiscally responsible" as synonyms, whether we like it or not.