Like everything else ...
... Tor is safe to use for people who know what it is, and therefore how it can be used appropriately and safely. It's not like the documentation is light on warnings about what can be seen at exit nodes, although that should be obvious anyway.
When using Tor, bear in mind that someone else can see your traffic, but not where it came from and where it's going. If I send an HTTP request via Tor, the content of the request itself and the content of the response will be easy to intercept at the exit node.
Encryption helps but as the article mentions it's not perfect if it is subject to man-in-the-middle attacks since the exit node can still have a snoop.
Tor is for anonymity. If you are sending password or credit card information you are volunteering to sacrifice your anonymity to the system you are sending that information to. While there are conceivable example where you might want to identify yourself to the destination system and still use Tor, they are few and far between.