Many of the hundreds of thousands of Hispanic demonstrators who poured out into US streets on April 10 may not know much English, but they've learned the language of American politics: Flags. Tons of flags. And make them American. That last detail was lost on the first wave of protesters two weeks earlier whose highly televised demonstrations were distinguished by the ubiquity of Mexican flags. Poor salesmanship. If you are appealing to Americans to give you the rights and privileges of citizenship, it is not a very good idea to hail Mexico, and an even worse idea to hold up signs such as "This is our continent, not yours!" and "Honkies are illegal aliens too.'' But by April 10, the demonstrators were as American as apple pie. All stars-and-stripes and white T-shirts, a nice additional touch, painting the television screen with the color of peace and brotherhood. As one demonstrator explained, "I think we have been somewhat educated." And so they have. They are now reading from the original civil rights textbook written by Martin Luther King, whose genius was to ensure that his people's struggle was always expressed in quintessentially American terms. There was nothing cynical or contrived about it. Of course it was good politics, but King was passionate in his belief in America and in the belief that the struggle for black equality was a fulfillment of America's true creed. Which is why King spoke naturally, if pointedly, in classic American cadences, invoking the sacred language of Lincoln, the Declaration and Exodus. BUT IT is not enough to speak in the right cadences. You need to know how to articulate and frame your goals. Americans instinctively know the difference between these two civil rights crusades. Blacks were owed. For centuries they had been the victims of a historic national crime. The principal crime involved in the immigrant crusade is the violation of immigration laws by the illegals themselves. To be sure, that is not a high crime. But it does not behoove one who has stealthily stolen into another's house to then make demands about rights - or to march under the banner of "The National Day of Action for Immigrant Justice." Justice? On what grounds do those who come into a country illegally claim rights? They seek good will and understanding. And Americans might give it - but on request, not on demand. Martin Luther King had a case for justice that was utterly incontrovertible, yet he always appealed to the better angels of America's nature. It is all the more important for illegals, whose claims rest not on justice but on compassion, to appeal to American generosity, openness and idealism. There is much generosity in America to be tapped. But that will require two things. First, a change of tone. And second, a clarification of goals. If you find a stranger living in your basement, you would be far more inclined to let him stay if he assured you that his ultimate intent is just to improve his own life and not to prepare the way for his various cousins waiting on the other side of your fence. And that's the critical issue that the demonstrators and their supporters ignore. Is the amnesty they are demanding/requesting the beginning or the end? Is it a precedent or a one-time - last time - exception? Are they seeking open-ended immigration or do they agree that they should be the last wave of illegals? We know they support the spirit of the failed Senate bill which, when all the phony length-of-stay distinctions are stripped away, is about legalization and amnesty. And we know they oppose the House bill because it declares illegals to be felons. But House Republicans recognize that they made a huge political error with that language and are pledged to remove it. Will the demonstrators support the rest of the House bill, which would radically restrain new illegal immigration by means of a physical barrier and other measures? If the answer to that is yes, then we have the makings of a national consensus to combine the House and Senate bills - a fence plus amnesty - into a comprehensive new policy. But we need an answer. The Hispanic civil rights movement is young and lacking unified leadership. That would be an excuse for temporary incoherence about goals if the massive demonstrations did not insist on bringing the issue to a head now. The politically mobilized millions need to tell America where they stand: Are they ready to be welcomed into the American family as the last illegals - or only as the first of many millions more? The writer is a syndicated columnist for The Washington Post.