President Ferdinand E. Marcos warned today of a new crackdown on businessmen who recently have joined the opposition forces in staging protests against his government.

Marcos, in a special television message, also warned Catholic school teachers to cease teaching what he referred to as "hatred" of the government in their classes.

In one of the toughest declarations since a series of antigovernment protests began, Marcos said some businessmen have been identified in pictures taken during demonstrations. "Some businessmen think that they can find sanctuary in the tall buildings of Makati," Marcos said, warning that they would be sought out by agents assigned to locate them.

Makati is the commercial and financial center of Manila and the scene of several anti-Marcos demonstrations since the assassination one months ago of Marcos' rival Benigno S. Aquino Jr.

Police used tear gas there Friday to break up one protest. Marcos specifically named several banks and the Ayala Foundation, the executives of which he apparently suspects of having participated in the rallies.

Marcos also warned that the government's policy of using "maximum tolerance" in combating street demonstrations has been discarded.

From now on, he said, force would be used if demonstrations become violent.

The military announced yesterday that it would revive a martial-law practice of establishing checkpoints to investigate vehicles entering Manila and other cities. Marcos said today this step was necessary to prevent communist guerrillas from entering Manila to foment trouble.

Yesterday, military authorities charged 52 people with "sedition and inciting rebellion," and Cardinal Jaime Sin, the Catholic archbishop of Manila warned that, barring immediate liberalization, "bloody revolution" was imminent in the Philippines.

In the southern city of Davao, terrorists hurled grenades into a crowd watching a beauty pageant. At least 12 people were killed and more than 200 wounded, United Press International reported.

Police officials said at least two fragmentation grenades exploded near a wooden stage erected in the courtyard of the Agbao municipal hall in Davao, 600 miles south of Manila.

[Police said the grenades were hurled from a speeding car, and blamed the attack on the communist New People's Army.]