Not to mention that the implication of the message is basically, "You have to stick this out." It's a violent reassignment of guilt. And yeah, maybe your mom did come around to accept you for who you are eventually, but what actually matters is if she does not love you now, when you are at a vulnerable time in your life.
The fact of the matter is that it does not get better for many people, especially the poor, minorities, and transpeople. The latter has a suicide rate three times higher than the rest of the population. Dan Savage is treating anti-LGBT bullying as "Oh, well as soon as you get out of college you can just grow up, move to Seattle, take a trip to Paris, and adopt a baby! It's just so simple!" No, no it's not.