Of course when you speak to a large crowd you use a technique conform to your intention. The argument in this case will be subject to will. You can be nice, hard, blunt, bend truth or just instill an 'us vs them' which is mostly the best trick to get them on your side. Nice examples are speeches of leaders of today or even of the past, like Hitler or Goebbels. Large crowds require some notion of propaganda.
Individually you can use whatever technique you see fit. I don't think you need to be nice and subtle to get a point across. Most people aren't that different from children and submit to authority or rely heavily on what others think of them. You overpower them and they will borrow your arguments. Of course, they'll change ideas again when being confronted by the next authority. To some that might matter but if you classify people in a 'worthy' and 'unworthy' manner, who cares?
On a forum it is purely about the argument. Therefor I find the best approach to use whatever the argument needs. Even totally crushing to get rid of the shit is valid. Like I said, it's memetic warfare and as long as an argument is solid or strong enough, it is valuable. The moment it fails, one can look at why it fails and improve.