People who are not very smart or who are easily convinced to do things.
Calling someone softheads is not very nice.
Examples:
The softheads believe everything they hear.
Don't be such softheads and fall for that trick.
The softheads in the story always make the wrong choice.
The softheads thought the joke was real.
Some people are such softheads that they believe anything.
The softheads in the movie were always getting into trouble.