Unless Congress passes a law making it not mandatory, yes it is.
en.wikipedia.org
"Social Security and Medicare expenditures are funded by permanent appropriations and so are considered mandatory spending according to the 1997 Budget Enforcement Act (BEA). Social Security and Medicare are sometimes called "entitlements," because people meeting relevant eligibility requirements are legally entitled to benefits, although most pay taxes into these programs throughout their working lives.
Some programs, such as Food Stamps, are appropriated entitlements. Some mandatory spending, such as Congressional salaries, is not part of any entitlement program. Funds to make federal interest payments have been automatically appropriated since 1847."
Again your opinion of the spending is irrelevant.