The second circumstance is when you have a runaway viral hit on Google+ and make the "What's Hot" list. That moves the post to the Google+ "front page" where trolls might jump into your conversation.
In both the YouTube and the What's Hot situations, it might not be worth the trouble to block trolls because they're probably transient. They'll troll that one post, but likely won't come back to bug you later. If they do, then just block them, mute them and/or flag their comments.
It's all about great conversations
By blocking trolls, while simultaneously cultivating conversation around your interests, you end up having the most amazing conversations, making the most amazing friends and having the most amazing time.
These are not actions you do once, then forget about. If you make it a daily ritual to engage with the interesting people and block or flag the trolls, you'll eventually end up with a whole lot of constructive, interesting and fun people in your circles -- and no trolls, haters and bullies.
You don't have to put up with trolls. Just move to Google+ and shut them down.
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