FRANKLY, WE LIKED the administration's Rhodesia/Zimbabwe policy better before the president dropped in on Nigeria. A month ago, for instance, soon after Ian Smith agreed to turn over power to an elected majority-rule government later this year, the administration was still complaining that he had not opened the door to the guerrillas sworn to destroy him. But there was, too, recognition that the agreement between Mr. Smith and "internal" black nationalists reflected "some progress . . . a step in the right direction" - as, of course, it did.

In Lagos, however, Mr. Carter seems to have succumbed to Nigeria's uncomplicated fervor for a Popular Front guerrilla victory. The final communique omitted any mention of progress in Salisbury, though a multiracial interim government now actually exists there. Rather, the communique (signed for Nigeria by its unelected military leader) pronounced the internal procedure "unacceptable as it does not guarantee a genuine transfer of power to the majority" - as though the guerillas, who have refused to settle for the share of power they might expect to win in elections, will consummate "a genuine transfer of power to the majority" if they win by force of arms.

We understand that the administration seeks to draw internal and external forces together, the better to bring peace to Zimbabwe, preempt Cuban-Soviet intervention, and show South Africa that peacable change works passably well. Those are worthy purposes. But Mr. Carter's pursuit of them can be painful. Virtually all his rhetoric favors the external people. He holds Salisbury to lofty moral and political standards, while often appearing to wink at failings of the Popular Front. He refuses to say the one thing that might most clear the air: that if the guerrillas reject a fair opportunity to come home while Salisbury moves to honest majority rule, the United States will go with Salisbury. His performance is all the more baffling when you consider that the internal settlement looks to be more democratic, moderate and multiracial than any government the guerrillas might construct.

Does the United States gain respect for itself and a hearing for its policies - among internal or external Rhodesians, in Nigeria or elsewhere in Africa - by conveying an impression that it will do practically anything to win liberationist credentials? We doubt it, and we think the president doubts it, too. Indeed, in Lagos he conspicuously did not do the easy, popular-in-Africa thing with respect to South Africa, choosing instead to affirm the United States' own, less militant policy. His hosts did not like it, and said so. But on their part, they withheld any real support for the American effort to limit Soviet-Cuban intervention in Africa. Such candor - and continued discussion - is what good friends, especially those trying to become better friends, owe each other. It should be applied to Rhodesia, too.