The slaying this week of three kidnaping victims -- two Britons and an American -- in Lebanon was a sharp reminder that for many in the Arab world terrorism has become a recognized form of unorthodox warfare wielded by the weak against the powerful.

But the deaths also testified to a growing perception in this region that governments are increasingly willing to risk the lives of individual citizens in the name of the higher interests of the state.

Conversations this week with ordinary Middle Easterners, western and Arab diplomats and other analysts made clear that no disclaimers from Washington or London are likely to persuade them that the U.S. and British governments could have ignored the fact that all western hostages in Lebanon were at risk as a result of the air raids against Libya.

Such realpolitik is not new for the United States. Soon after the abortive rescue operation in Iran in 1980, a U.S. ambassador let it be known that Washington expected at least a third of the Americans held at the embassy in Tehran to be killed.

But now concern is growing that the Reagan administration is so buoyed by American public backing for the show of force early Tuesday that it has discarded evidence suggesting that terrorists are undeterred by such military displays.

Some regional specialists inside and outside government are convinced that terrorists and those who employ them thrive on displays of sophisticated western technology typified by the Iranian rescue attempt and the Libyan raids.

Adding to concern about what many normally pro-American moderate Arab governments construe as the Reagan administration's other misguided policies in the Middle East is the widespread fear expressed privately that they may be brought down in the wreckage caused by American muscle flexing.

Whether failed, as in Iran, or more technically proficient, as in Libya, these American shows of force provide the stuff of myth making. They allow the weak to be seen testing their mettle against the world's most technologically advanced military power.

Just before the U.S. air raids against Libya, a high-ranking Algerian official privately warned against launching such an attack, saying, "You Americans must realize that [Libyan leader Muammar] Qaddafi will disappear one day, but that the humiliation you inflict on the Libyan people will live on and on."

Such arguments may strike western minds as illogical, but the single-minded dedication of terrorists willing to lay down their lives for their cause is a matter of record.

Moreover, a case is often made that the use of highly sophisticated U.S. weaponry in the Middle East, by the very scale of devastation it causes, helps recruit more terrorists.

Israeli specialists, among others, have argued that their Army's invasion of Lebanon in 1982 boosted Palestinian terrorism by forcing the Palestine Liberation Organization's political headquarters out of Beirut, blunting its diplomatic successes.

Responsibility for various terrorist acts has been asserted by groups who said they were avenging the 1982 massacre of Palestinian civilians in west Beirut's Sabra and Shatila refugee camps.

Although the slaughter was carried out by Christian Lebanese militiamen, many Arabs blamed Israel for not stopping the atrocity and criticized Washington for not preventing Israeli troops from invading west Beirut in violation of formal promises to the United States.

Last June, when Lebanese Shiite terrorists hijacked TWA Flight 847 and kept its passengers hostage for more than two weeks in Beirut, they invoked the U.S. 6th Fleet's salvos against Lebanon in 1983 to justify their action. Such use of massive western firepower contributes to resentment and retaliation against vestiges of western influence in the Middle East.

The three hostages killed in Lebanon had chosen to remain in predominantly Moslem west Beirut, where two were teachers and the third a librarian at the American University of Beirut.

From one end of the Arab world to the other, U.S. diplomats privately express their misgivings about serving a policy that puts at risk their own lives as well as what they perceive as American national interests in the region. Some complain that their advice is neither welcomed nor acted upon in Washington.

"The way things are going, the United States might as well close its embassies in the Arab world," one western diplomat said, "and let those Arabs who still want to do business conduct it in Washington. That would cost less than the hundreds of millions being spent to upgrade security at American embassies."

Such sentiments are fueled by an increasing number of ambassadors in the region who lack Middle East expertise, some observers say. In recent years, more and more ambassadors who were regional specialists have spoken out against U.S. policy -- but only after their retirement.

Some Arab and western diplomats suggest the United States would be better served by training its own specialists to fight terror with terror.