Most people sharing a prejudice during a time in the past doesn't make them right. It might make it understandable, but not right. Slavery in the US was "understandable" and accepted by too many during the time it was practiced, but definitely not right, then or now. I agree that most Germans in WWII, most whites in the USA south during the era of slavery, and most people in England who supported government rules against gays, along with numerous other people who played a part in various sad chapters in history, are not necessarily "bad" people. But the actions were bad, regardless of whether the people themselves were good or not.
As Gordon Brown stated in the official apology for Turing's actions, delivered sadly too late in 2009, "Thousands of people have come together to demand justice for Alan Turing and recognition of the appalling way he was treated. While Turing was dealt with under the law of the time, and we can't put the clock back, his treatment was of course utterly unfair, and I am pleased to have the chance to say how deeply sorry I and we all are for what happened to him. Alan and the many thousands of other gay men who were convicted, as he was convicted, under homophobic laws, were treated terribly. Over the years, millions more lived in fear in conviction. I am proud that those days are gone and that in the past 12 years this Government has done so much to make life fairer and more equal for our LGBT community. This recognition of Alan's status as one of Britain's most famous victims of homophobia is another step towards equality, and long overdue."
I'd add "all that is necessary for the triumph of evil is that good men do nothing." I agree you can be good and do nothing, but I also agree that it's better to stand up for others.