If they're your friends, then you've presumably already gained their approval and respect, and they (hopefully) won't be bullying or insulting you, or if they do, because you're friends you realize they are only joking around. The are not strangers, even if you've never met them in person.
My sarcastic comment was for those that are not friends, those that do get offended by comments made by random people on the internet, and no, I don't believe we should react differently online or off. If you come to a group of people, and they start insulting you, I would expect the average person to walk away, and not try to defend their self against what amounts to a bunch of random strangers. If it is instead the stranger that has come into your circle of friends and started insulting you, ignoring them usually works quite well.
When the same situation happens online, you get a different response; the insulted party often stays, attempting to counter the insult. Even when the person doing the insulting is the new person who has stumbled into the group or a person well known for their pointless insults, there's still the urge by some to argue themselves. Just ignore the insulter, or walk away from the group you were not invited to, or if the insult is the result of a mistake you made, learn from it.