Don't confuse Tackling with Aggressivity.
Hard tackling just increase the amount of tackles during the match to +20 usually, and low tackling reduce them arround 10-12.
But the aggressivity is set internally, you can't reduce this via normal settings, it is like a role assigned to make your team look realistic.
I've had some players like these, ot's quite easy to identify them. Now you have to see if it's worth to keep them, or if they just bring you more problems than benefits.