You can be unbanned tomorrow, I just don't want to see this happening again.
Staff rarely catch griefers when its later discovered, and its a big task to make sure old builds on most the maps are always protected, for whatever reason things become unprotected. Maybe the building, town etc didn't look all that good to you, but making more of a mess of it isn't cool.
Might not mean much to you, you might not even take much from an existing base, however it just encourages someone else to treat the buildings/towns the same way and further make a mess of the area because they saw it looked griefed already. Then we get the player of that building/town complain about greifing, maybe months later with no logblock record to show who did it. Its also nice to visit old maps and see what was built INTACT, not in an effing mess.
So consider the tempban you got a warning you have been a good player without any previous trouble, don't carry on greifing... if you want to help, let staff know if you come across a buildings/towns on the maps that are not protected so they can be. Obviously dirt shacks and wood box housing isn't the type of stuff that will get protected by staff, however unless you are going to clear the area or build there yourself, best to just leave it.