Why does my dynamic IEqualityComparer not work?

I have a class

public class Foo
{
  public int ID { get; set; }
}

and I've implemented a LinqEqualityComparer to allow dynamic IEqualityComparer tests for the Except extenion method.

public class LinqEqualityComparer<T> : IEqualityComparer<T>
{
    protected Func<T, T, bool> Comparison { get; set; }

    public LinqEqualityComparer(Func<T, T, bool> comparison)
    {
        Comparison = comparison;
    }

    public bool Equals(T x, T y)
    {
        return Comparison(x, y);
    }


    public int GetHashCode(T obj)
    {
        return obj.GetHashCode();
    }
}

I've created the following code to test it:

IEnumerable<Foo> settings = new Foo[]
{
  new Foo{ID = 1},
  new Foo{ID = 2}
};
IEnumerable<Foo> currentSettings = new Foo[]
{
  new Foo{ID = 1},
  new Foo{ID = 2},
  new Foo{ID = 3}
};
IEqualityComparer<Foo> comparer = new LinqEqualityComparer<Foo>((x, y) => x.ID == y.ID);
IEnumerable<Foo> missing = currentSettings.Except(settings, comparer);

However Foos 1,2 and 3 are all present in the 'missing' variable.

Why does this LinqEqualityComparer not work?