I find that when I boil the turnips in water the bitterness of the turnips goes away.
The boiling water removes the bitter taste of the turnips and they taste better boiled and are easier to eat when the turnips are boiled as well.
You can also add some salt to the boiling water when boiling the turnips which helps to get rid of the bitterness of turnips.
Or you can add some spices or mix the turnips within some stew or soups and add other flavoring to the turnips and you shouldn't taste the bitterness of the turnips anymore.
Adding potatoes into the boiling water along with the turnips as well as using salt in the water can make the bitterness of turnips go away even more.