Kinda impossible seeing as how people keep comparing Blockland to Minecraft.
Anyways, I would keep things positive if I could even comment :/
As Badspot said. If someone posts something silly, like "Minecraft clone", then just ignore them.
Ignoring them means you don't have to be rude, angry or abusive; Negative.
Instead, post only to show your support for Blockland, or to politely answer serious questions; Positive.
And if you're the sort of person who is likely to get exceedingly fed up with a few people saying silly things, and are likely to post out of anger, then simply avoid the Greenlight page.
Go on it once and vote for Blockland, and then don't return. There is nothing there for you but arguments.
You can no longer see the progress bar, so you've got no reason to return if you're likely to get angry.
If you want news on how Blockland is doing on Greenlight, then simply visit this topic and post in just this.
Don't worry yourself about a few comments by people who aren't likely to know what they're really talking about.