Cuban exiles living in Miami came to the United States for freedom of speech, but they're learning that it's best to keep their mouths shut, especially if they advocate anything less than the violent overthrow of Fidel Castro.

There is a feeling in Miami's Little Havana, as oppressive as the hot summer weather, that Cuban Americans should toe a rabidly anti-Castro line. And if they don't, they are likely to be publicly censured by those who do. Or worse, they could be firebombed.

Ramon Cernuda, a Cuban-born publisher and art collector, knows the cost of independent thinking. Last month, the art museum he operates was bombed. Federal investigators believe he may have been targeted because of his moderate views on U.S.-Cuba relations.

The FBI is investigating 17 such incidents that have occurred in Miami in the last three years -- most against Cuban Americans who don't subscribe to the vehement anti-Castro doctrine.

The keeper of the anti-Castro flame is the Cuban American National Foundation, which is based in Miami. We reported recently on the group's heavy-handed influence in Washington, where it hands out substantial political contributions and lobbies for a hard-line approach toward Cuba.

The group has condemned the terrorist attacks including the bombing of Cernuda's gallery.

Led by Jorge Mas Canosa, the foundation views itself as the true representative of Cuban Americans. But it doesn't have much time for exiles who support dialogue with Cuba. Mas Canosa has implied that those who disagree with him are close to Castro.

Mas Canosa renounces violence, but we have learned that the foundation has added to its ranks two brothers who were once members of the violent Cuban Nationalist Movement.

Guillermo and Ignacio Novo were recently assigned duties on the "information commission" of the foundation. The commission's job is to generate better public relations in Miami.

The foundation could have picked better PR men. The Novo brothers were convicted and then acquitted in the 1976 murder in Washington of Orlando Letelier, the former Chilean ambassador to the United States. Letelier was living in semi-exile in the United States because of his open opposition to Chilean dictator Augusto Pinochet. At the time, some Cuban exiles looked to Pinochet for leadership in overthrowing Marxist governments in Latin America, including Cuba. The Novo brothers eventually were granted a new trial by an appeals court and were found not guilty.

Some of their other exploits were highlighted in the book "Assassination on Embassy Row," a detailed account of the Letelier murder written by John Dinges and Saul Landau. According to the authors, Guillermo Novo, in 1964, fired a bazooka at the United Nations headquarters in New York to protest the presence of a Cuban banking official there.

Guillermo Novo told our associate Scott Sleek that he doesn't regret any of his past activities, and he wrote off the bazooka attack to the enthusiasm of youth.