This is true. Words like "shit" (くそ) exist, which is fairly tame compared to other languages. One of the worst phrases you can say is basically the command "die" (死ね).

When "cursing" at someone in Japanese, it's more about inflection, tone, and using the social status constructs of the language to talk down to someone. Such as the insanely informal Kansai dialect below:

お前、何をやてねん？！あほやで！ "What are you doing?! Stupid!"

Translated it's pretty tame, but depending on the context this could be quite shocking to the receiver.