The brother of slain opposition leader Benigno Aquino warned Sunday it would be ''very dangerous'' for President Reagan to visit the Philippines. Agapito ''Butz'' Aquino made the comment to reporters during a rally kicking off a nationwide passive resistance campaign aimed at ousting President Ferdinand Marcos. He said many Filipinos would view Reagan's visit as a show of political support for Marcos, whom they hold at least indirectly responsible for his brother's assassination Aug. 21 at Manila International Airport.
On Saturday, Marcos announced the release of 37 out of more than 500 political prisoners. Government critics and human rights groups said the order was a poor attempt to placate growing opposition to his 18-year rule. In response, Marcos reportedly asked, ''What do they think the government is, a chicken house they can change any time?''