I don't know who exactly is responsible for this dopey meme: 2 rainbow-colored hands are held together to make a heart shape, and the caption reads:
"WHEN DID USING YOUR RELIGIOUS BELIEFS TO DISCRIMINATE AGAINST OTHER BECOME A CHRISTIAN VALUE? CHOOSE LOVE."
But to answer the question: it started pretty early. It was already underway when Paul wrote his earliest New Testament texts, around AD 50. It's hard to know exactly when it began. To say that the earliest history of Christianity is hazy is a huge understatement. I haven't stopped investigating it, and I'm still not at sure about details such as whether or not Jesus actually existed, or whether Paul or someone else invented him.
*Sigh*. Yes, there are also non-judgmental Christians. Maybe there have been non-judgmental Christians for as long as there have been Christians. Maybe Jesus really existed and maybe Matthew 7:1 is an accurate quote from him. ("Judge not, that ye be not judged.") But there were also the other kind all along, starting very early.
Are some people somewhere on Earth actually so sheltered that they don't know about judgmental Christians? Maybe in the middle of China somewhere, out in the boonies. Maybe. But there seem to be people with selective perception everywhere you turn. Especially when it comes to religion. People who do mean things, or nice things, or what have you, are not the REAL Christians, or Muslims, or what have you, depending upon what variation of the No True Scotsman fallacy you are committing and which religion you are boosting or attacking.
Maybe the old advise never to discuss sex, politics or religion in public wasn't meant so much to protect sensitive people from being offended, but to protect intelligent people from being disgusted.