I suppose it depends on why you are arguing online.
If the real reason is to challenge your beliefs, you may need to ask if this is consistently happening in the communities you visit and if it isn't, you might need to find better online communities or engage in some practice other than arguing online to challenge your beliefs.
If there are other reasons that arguing online appeals to you, it would be worthwhile to identify them.
Arguing online can be relatively cheap (easy to get into many arguments with a low initial investment and a lowered chance of it affecting your world offline) way to get arguments. However, if you are concerned about the quality of the arguments you are having, it might be worth investing more time into finding good places to argue or abandon arguing online for someplace where the low-hanging fruit is a little higher quality.
I wont be the only one here who "wastes time" arguing about things they care about online (note: I am referring to web forums and things like subreddits, I am not including Less Wrong whose dynamic is completely different). It seems like something that is worth optimising in some direction.
The theory behind it is that one should expose themselves to counter-arguments allowing their claims to be attacked so they that have a chance to substantiate them or reject them upon realising they are mistaken.
In practice they generally follow a pattern that starts with people pointing out what they believe are mistakes then ignoring or intentionally misunderstanding the other party when he refutes or backs up claims.. and ends up with insults, patronising sarcastic remarks and nobody changing their mind about anything.
I don't particularly care about changing other peoples minds to make them agree with me (well, it would be great but I think it's practically impossible) so one thing I would like is for both people to at least end up feeling good.
So I'm interested in three things: Do other LWers recognize this pattern now that I have mentioned it? What decision did those that were already aware of it make, in order to optimise this activity?