Organizers called for protection of children from 'LGBTQ terrorist propaganda agenda'
Hundreds arrested in Istanbul on Sunday
Istanbul officials sought to prevent event from happening
Organizers sharply criticized authorities' decision
Amnesty International condemned 'disturbing' Ankara crackdown
Defendants faced up to three years in prison
Journalist among 20 people detained on Saturday
Authorities recently arrested four members of militant group
Recent years saw expanded international coverage
Guyana, Jamaica among countries with LGBTI parades this year
