Don't want list of user which are blocked by user in list?

Table : user 
Id name
1   a
2   b
3   c
4   d

Table : block_user
id block_by block
1   1         2

when i retrieve list for user 1 at that time i don't want user 2 in list but i stuck at query: i want user 3 , 4 in place of it return user 2 which is blocked

my sql fiddle Fiddle here and my current query

Select u.* from user u JOIN block_user bu on bu.block_by = u.Id or bu.block = u.Id where u.Id != 1 GROUP BY u.Id