Since the Greeks themselves were the producers of the bulk of the written works surviving from the Classical period, it is very hard to know what non-Greeks thought at all, much less what they thought about the Greeks. Even for the Greeks themselves, controversy rages over what they really thought about pederasty. However, from what little material we have, it seems the Greek practice was fairly unique in its Eastern Mediterranean context. In his article 'Greek Homosexuality and Initiation' (1988), Kenneth Dover sums up what we know:

If we look at the ancient civilizations of the eastern Mediterranean and Middle East, acknowledging that as yet we do not know anything about the Babylonian and Hittite attitudes to sexuality, we find that homosexual copulation was treated in Egypt as a sin from which the soul after death needed to be purified, in Israel as a grave sin meriting death, and in Assyria as a crime incurring savage punishment.

The great exception to this general situation appears to be the ancient Persians, who typically had a far more prudish attitude to nudity and sexuality than the Greeks, but who allegedly picked up the habit of pederasty from the Greeks:

But the Persians more than all men welcome foreign customs. They wear the Median dress, thinking it more beautiful than their own, and the Egyptian cuirass in war. Their luxurious practices are of all kinds, and all borrowed: the Greeks taught them sexual relations with boys.

-- Herodotos 1.135

However, we don't know for sure if Herodotos' claim is accurate. The Medes are notoriously archaeologically invisible and may never have existed; the Persians did not wear Egyptian armour, unless the common linen cuirass is meant. This leaves us with little confidence that the third of the habits mentioned was something borrowed by the Persians either.

It seems likely that most peoples the Greeks encountered would have found their pederastic practices either quaint or abhorrent. Then again, this may have been true within Greek society as well; pederasty was primarily an elite phenomenon, and it is possible that the common people did not think well of the whole thing. Again, our problem as historians is that their voice does not survive.