The "is" is wrong in it. Otherwise, it's not uncommon with a suitable modal verb instead (of the "is").This is best be avoided.
Bears are best avoided.
And I cannot [STRIKE]say[/STRIKE] come up with/write a sentence with the "be avoided" version; I don't know where I got it from.
Bears are best avoided?
That could be reworded as "Bears best be avoided"