The modern concept of homosexuality didn't exist in ancient Greece. Pederasty and sex with male slaves were the only acceptable and widely practiced homosexual behaviors during those times. It's only tolerated so long as a free born took on the active male sexual role and the slave/young boy took the passive female role. And it's not even a permanent way of life. Every male was still expected to marry and have children. It's not true that "a lot of people were having sex with both the same and the opposite sex." That priviledge was only enjoyed by those belonging in the upper class. That's why the large majority of recorded evidence of homosexuality in the ancient world is about royalty and the people in power.