BACK WHEN SOUTHERN STATES were fighting school desegregation, I used to wonder what what it would be like to be black and have my tax money used to keep me deprived of my rights. I think I am about to find out.

I bring this up now because a fellow named Lyndon H. LaRouche Jr. has applied for federal matching funds for his presidential campaign. Until November, LaRoche was the head of the U.S. Labor Party, which began life, as did so many of us on the policical left but has since gone so far in the opposite direction that to call it politically right is to slander the entire conservative movement.

Suffice it to say that the party is authoritarian and anti-Semitic and some other things as well. The first two are enough for me. I don't want my tax money to support the policical campaign of Lyndon LaRouche.

LaRouche believes, according to party publications, that "Zionist circles funded the founding and continuation of the American Nazi Party," that he is targeted for assassination, and that the chief conspirator against LaRouche is none other than President Carter's national security adviser, Zbigniew Brzezinski. He replaces the queen of England.

At the moment, LaRoche's application for matching funds is before the Federal Elections Commission. In 1976, LaRouche also applied for matching funds, but since he was the only primary candidate of his personal political party, the FEC said no dice. LaRouche sued the FEC and lost. This year, he has come back as a Demmocrat. Clever, that LaRouche..

The Democratic Party, you see, does have more than one candidate. And in order to qualify for matching funds, all you have to do is file your candidacy and then raise $100,000 in contributions of $250 or less with $5,000 coming from 20 different states. This sounds complicated, but all you need, really, is 20 people in 20 states willing to fork over $250 each. For the U.S. Labor Party, to which LaRouche formerly belonged, this would not be so difficult. The organizations's budget this year is estimated at something like $4 million.

The idea behind having the government provide matching funds was to reduce the influence of the fat cats. This was yet another post-Watergate reform. Coupled with full disclosure and limitations on personal political giving, it severely changed the rules of the American political game. It is also, by and large, a lovely idea -- especially full disclosure.

But there are some problems. One of them is that it makes it harder for a worthy, but littleknown, candidate to raise money. He can't do what Eugene McCarthy did in 1968 -- turn to a few very wealthy men to raise seed money. Candidates must now show a broader base of support, which is just another way of saying that they have to be more popular.

John Connally has shown, however, that you cannot keep Big Money in its place. He has rejected matching funds. The candidate of the board room has argued that he needs to spend more to catch up with his chief rival, Ronald Reagan, who after all has been runnng for the Republican nomination since what seems like time immemorial -- at least since "Death Valley Days." You don't have to be a Connally fan to understand his logic. I, for one, don't care how much he spends just as long as I know where the money is coming from.

It is LaRouche who bothers me. The law, having failed to keep Big Money in its place, has now managed to underwrite the political aspirations of the likes of Lyndon LaRouche. He is not about to become president and he probably won't run well enough in the primaries to continue to receive matching funds (you can't get less than 10 percent of the vote in two primaries back to back), but he is going to get a hunk of our tax money -- several hundred thousand dollars, probably, to spread the sort of message found in his party publications.

I liked it better in the old days. LaRouche has a perfect right to write what he wants and say what he wants and even run for president. Let him do what he wants.

But not on my buck.