Well why did you post at all op?
Everyone who has seen it is saying it is not in the same vein as the other films and so does the rating
But you are deternined your ever so mature 3 yr old can deal with death and destruction so why bother asking?
It is not a cozy little super hero film it is much darker and more adult themed. I dont know any 3yr old who needs to see that or could 'understand' many of the themes in the film.
Let kids be kids for goodness sake, plenty time for other age rated films when they are old enough
Sometimes as parents we need to say "No its not for little kids." Its really not that hard to protect your childs innocence for a bit longer.