I think a disctinction needs to be made between what monastics sometimes say, and what secular Fathers say. The monks are usually talking about leading the perfect, perfectly christocentric, life, and not things being "good" and "bad" in the way we would think of "good" and "bad". To a monastic, anything
that takes away your mind from the contemplation of (or interaction with) God is a lesser good. Marriage itself then, according to some Fathers, is "despised" by Virgins and Monks. Why? Not because it is sinful in itself (numerous Church canons condemn the belief that marriage is sinful), but just because it is a lesser good. Monasticism and virginity are the higher callings, and as Saint Paul points out, allow us to fully focus on God, while in marriage we have a responsibility to worry about earthly affairs. In that way, monks can speak of many things as being things to avoid, while the same things aren't necessarily avoided by those of us living in the world.
I think you're correct, Dmitri, in saying that Aquinas wasn't the first (though I don't think that was what Bobby meant?
) The west in general has always taken a darker view of sexual intercourse. It was those in the west, for instance, that had the first council to instruct clergy to be celibate, and the first to propose Church-wide celibacy at an Ecumenical Council (the first Ecumenical Council -- ironically, clerical marriage was defended by the monk Paphnutius). Later, during Photius' time, when western and eastern Priests were arguing over jurisdiction in Bulgaria, one of the major charges against the eastern Priests were that they--horror of horrors!--had wives! They hoped that the celibacy of the western Priests in Bulgaria was seen to be a sign of their moral and doctrinal purity. And of course, it later became a mandatory practice for those in the Roman Rite (proper term?). Many early Fathers were--by modern American standards--closed minded, but the general thought on this issue in the west seems to have come from Augustine (Didn't Thomas Aquinas say that he wanted to be know as an Augustinian? I seem to recall that somewhere). In the east, for instance, pleasure experienced during sex wasn't considered a sin unless it was sexual conduct motivated by lust. In other words, it wasn't wrong to enjoy it if you were following the Church's guidelines. In the west this view of enjoying sex--even in a "correct" context--wasn't always approved of. Just some thoughts from what I've read; If I'm wrong on something someone please correct me!
PS. I don't mean to be attacking "the west" here in general, as is sometimes the case in Orthodox polemics, where it seems like "the west" in its entirety is worthless. I'm only trying to explain how I see things regarding this particular issue. Were we talking about christological controversies in the 6th century, I would perhaps be speaking against "the east" collectively