Firstly, Adventure is PVP, Creative is PVE. So in PVP you walked into an enemy town and that is why the templars attacked.
Secondly, public servers have an admin who spent many many many hours setting up the server to be how they want before making it so people can join.
Unfortunately the game itself isn't set up for a single player in mind, the devs assumed people who wanted to play by themselves would also want to set up everything themselves.
You could start up a Creative server and not get attacked by templars, as for set up starter towns and so on, yeah you would need to do that yourself if you intend to go single player.
If you want to walk into a server that is set up and ready to play then you will probably need to log in to a public server.
Hope this helps in some way.