Am I just not finding the option or do the forums actually lack the option to disable smilies? Most forums have an option to get rid of the graphical smilies, so that you don't see when other people use them or when you type one in.
You can suppress the display of smilies if you're willing to suppress the display of other images too. This is done by unchecking the Show Images checkbox in your User Options. If you do this then images won't display and you'll see URLs instead.
There isn't a setting to disable smilie displays and leave other types of images.
You can disable the interpretation of the ASCII codes for smilies when you post but you can't disable the display of smilies that other users insert into their posts:
If you check the Disable smilies in text checkbox when you post then the characters will be treated as regular text.