MUGGLE/WIZARD RELATIONS

[bg87 at msn.com]

No: HPFGUIDX 30014

Obviously, the wizarding community goes to a lot of trouble to make 
sure that human beings have little knowledge of the wizarding world, 
with the use of memory charms.  However, there are some Muggles with 
extensive knowledge of the Wizarding world, such as the Dursleys and 
Hermione's parents.  So I have 2 questions: 

1) How can it be ensured that the Muggles who have knowledge never 
pass it on to others?

2) Why don't the two communities interact and help each other?  It 
seems to me that the wizards could have been very useful in, for 
example, fighting WW 2.  Conversely, don't Muggles have the right to 
know that an insane wizard like Voldemort is on the loose, and 
couldn't they be enlisted in fighting him?  I assume that evil is not 
immune to Muggle weapons.