critical thinking

If we compare those two statements “Some pigeons are gentle birds” with”Some pigeons are not gentle birds.” It seems to me that they are contradictory statements. The second sentence negates the first sentence. We know that pigeons are beautiful, fancy, loyal, resilient, intelligent, and friendly, at the same time they are aggressive, and they are also disease indicators and indices of environmental health. Therefore, all pigeons are the same they are gentle birds, so maybe they can’t behave gently all the time, but it doesn’t mean that they are not gentle birds. Though there are different kinds of pigeons, they behave in the same way. Pigeons are symbols of peace and love. 

The second question is about “All amusement parks are fun-filled places” with “Some amusement parks dangerous places.” The first sentence is a valid statement, but the second statement is invalid because we cannot confirm that it is dangerous. I heard that the United States has dangerous amusement parks, why do people go there, if it is really dangerous?