Yes they can;
He wasn't spouting nonsense.
The problem is Haki is finite, thus using too much Haki everytime vs a Logia who also has strong Haki would be in disadvantage.
Thus not taking the attack is better rather than wasting Haki.
Thats why Teach wanted Darkness, he could nullify DF with Haki but when he has Darkness, he doesn't need to waste his Haki to do that. With Darkness, he can nullify DFs without wasting his Haki.