Republicans and conservatives hate Social Security because of the word "Social".
"Social", to them, means Socialism. This is why some of the more disingenuous on the right tend to compare Liberalism with Nazism, simply because the Nazis used the word "Socialist" in their party name. And "Socialism" means "Communism", in their minds. The Republicans are literally still fighting the Cold War. They're like the Japanese soldiers from WWII who were never told about the end of the war and kept fighting decades later. And they believe that everyone except their own leaders are secretly commies themselves, but in reality their leaders are capitalists, and it's in their financial best interests to keep the "war" going, so they never tell their troops to stand down.
This is why the George W. Bush administration was taken by surprise on 9/11; they were still only concerned about the "Rooskis"! Condoleeza Rice was supposed to make a report on the defense of the United States on 9/12. She never got to make it, obviously, but the content of that report has never been released. Those who have seen it, though, tell us that there was nothing about terrorism in it; it was all about Russia as a nuclear power and Star Wars.
But let's be fair to Condi; she wasn't quite as ignorant as all that; she'd hedged her bet. After the Al Queda-coordinated bombings at our embassies in Africa Clinton had decided to destroy Al-Queda. He asked Richard Clarke to come up with the plan for this. The plan was ready to go just before Clinton left office, but rather than hand Bush a war they decided to give the plan to the Bush administration and let them handle it. Rice was impressed with the plan, and with Clarke, and kept him on the new administration and slowly, very slowly, went over the plan and moved it up the ladder towards the President's signature. After 9 months, the plan had finally been approved by the last group before the President would see it; that was on September 4, already far too late to prevent the 9/11 attacks.
Do you remember Condi Rice ever telling us about the Al Queda threat? Neither do I.