JFK cut taxes, engaged in pre-emptive military actions against the communists, and told the country to ask not what the country can do for you. Those are Conservative values.
But yes, the Democrats who followed have destroyed this great country.
JFK gave us his lifelong goal of the 1965 Immigration Act which passed on his death, he unionized the government, created the homeless, was a complete idiot in foreign affairs and against the communists and he started the Vietnam war, and was a disaster as a president and was an incredibly sleazy and dishonest man who appears to have stolen the presidential election.
Reagan called him a Marxist in a private letter.
Not sure what you mean by "pre-emptive military actions against the communists?" He had anti-Communists murdered; undermined anti-Communist Governments in the Third World; and, as others have cited, advocated the immigration policy his brother put through in 1965, which favored those with no historic ties to Americans, over those seeking to come from traditional sources of American descent!
His Secretary of State sought to out-do the Communists in undermining the cultures of other nations. Is that what you consider "pre-emptive?" It was a clear violation of principles of the "Law of Nations," recognized for over two hundred years. (And see American Foreign Policy.)
Yes, he did have writers who could write speeches full of pretty slogans. That does not excuse his efforts to move America to the Left.