I can't say I'm AGAINST it, because I'm not. But, I DO tend to be a bit more skepitical about large age gaps in relationships.
Mainly, is it a HEALTHY relationship?
In general, people who are in certain stages of life are looking for a certain thing in a relationship. And those differences in age, plus the differences in the sex of the people in question can lead to some bad situations.
For instance, an average 45 year old man looking to date a 20-24 year old girl is looking for something different in a relationship than the normal 24 year old girl is.
Your average college aged girl is more focused on her life in general than just dating. If she's not in college, she may well be looking for something more financially stable than a girl who IS in college.
Men don't have the same biological clock was women either. I've seen many women date or marry someone younger than them and at the time the men were saying, "I don't want kids, I'm happy just with you" but 10 or so years pass and suddenly they're saying, "Hmmmm, maybe something more is what I really want".
This can lead to DEVASTATING break-ups where both feel like they've been cheated and lied to without either really doing anything overt to cause it.
I think I would raise an eyebrow to a 32 year old dating a 19 year old. My main question wouldn't be to the relationship as much as WHY hasn't your life changed much since you were 18? There are many cases where this isn't a bad thing, but there are also many cases where it IS. And if this 19 year old was a friend or family member of mine, my first instinct would be, "Uh....what are you doing and what's wrong with this guy that you're the person he's the most attracted to?"
Granted, over time, if it seemed healthy, I'd calm down. The eyebrow would be less raised if the age difference were 10 years or less. And, of course, age differences matter less the older you get. A 60 year old dating a 50 year old isn't as scandalous as a 30 year old dating a 20 year old or a 20 year old dating a 10 year old.
I think the bulk of it has to do with the age grouping of young people. 20 year olds dating 10 year olds, OBVIOUSLY wrong. Bump it up 10 years and you still have the stigma (at least in the US) of a 19 year old being fresh out of high school and still being 2 years away from being able to drink. At 40 and 30, you're doing better, however, there is still a small part of a 30 year old can easily have a baby where at 40 it gets more dangerous, at least for the woman.
These are BIG milestones in people's lives. Crossing these milestones almost a decade apart (certainly more) leaves others wondering if both parties can possibly REALLY WANT the same things or if they are in the relationship for selfish reasons.
I DO believe it can happen and does happen often. But, I think it's also normal for the loved ones of the parties to be, skeptical about it at first.