YOU MAY have read that the District of Columbia government is planning to subsidize special sightseeing deals for tourists this summer -- and you also may have wondered why a strapped city is shelling out for this service in competition with existing tourmobiles and private bus operations. So have the owners of these private services, who are complaining that the city's subsidizing of week-end and holiday service for family groups and tourists on Metro buses would be unfair. They have a point.

Arthur D. Lewis, president of the American Bus Association, has stated the bus operators' case bluntly and well in a letter to Mayor Barry: "At a time when there is talk of higher taxes for people who live in the District and Metro is considering a fare increase for the people who use it on a daily basis, I don't see how you justify basically duplicating -- and at considerable public expense -- a tourism service that is already being provided."

Neither do we. There is no question that tourists are important to the city's ecomomy, and it happens that private operators have invested quite a bit to promote tourism and provide good sightseeing services, not to mention tax revenues, for the city. But if the city takes away the peak summer business, private companies are likely to hurt.

If the city's finances were in far better shape or if Metro's bus fares in the District were outlandish, a case for this subsidy might be stronger. But how many tourists really skip our town because sightseeing tours cost to much? Or putting it the other way around, how many more will be lured here through word about a deal on Metro? Judging from the first wave of visitors this spring, Washington's red carpet is in good shape without any matching ink to make it look better.