Hello Mr J! The point is that you can use any of the ports for inputs. Its true that only port0 does not have internal pull-ups and it WILL float. Other will be pulled high. You WILL NOT damage a port if you write 1's to it and then pull it low externally. The current is limited by the internal pull-up.

If you write 0's to it and then pull it high, then you WILL damage the device.

You can always take necessary precautions for the risk of a damaged device.

Regards
Aman