What a great poem! We seem to have lost our way in the how we interact with each other, such disrespect and casual violence. Manners are far more important in the human condition than people realize.
Grammar issue: Manners is a plural word, and the first line of your poem treat them this way 'Manners are' instead of "Manners is' (wrong)
Then the 2nd and 4th line refer to 'It' ... seeming to be talking about manners, which since it is a plural word should be 'They'... 'they choose' ... 'they decide'
I agree with your words. Being polite and kind can open the door to friendship. Negative treatment of another close door and create separations. I like how you made your point in the poem. A outstanding poem.
Coyote
I believe in this golden line "God has created every human being to fulfil a particular and special role in this world".
I'm very fond of reading.. more..