It's not theft, it's a social program that used to not exist, and because of it not existing, life was so shit for old people that everyone was demanding something like it.
The idea that diligent investment in retirement savings might be a solution was rightly laughable, considering the Great Depression was going on. People who had retirement accounts they needed in 2001 and 2008 might tell you it still is laughable, but you can't piss and moan about that until it completely fucks your life at retirement and the only answer you get is "OH WELL" ¯(ツ)_/¯
Social Security would be 100% solvent for the next 75 years by making two changes: lift the income cap and apply the tax to investment income as well as regular income.
If you don't see benefits it will be so conservatives can continue to reduce the tax burden on the rich, full stop.
The military budget is bigger than Social Security and nobody bats a fucking eye - whether there's an R or a D next to their name. But yeah, we're the spending problem.
Edit: predictably, the military apologists come in to mention than "defense spending" is not as high as "social security," because of course "defense spending" doesn't include "veterans benefits" and isn't 100% discretionary and not at all paid for with a payroll tax. Get fucked, the lot of you.