It's not so much that more than 60 is bad for you, as that someone doing that much *might* be setting themselves up for failure, and *is* doing more than necessary.
For general health and weight loss, up to 60 minutes a day is recommended. It's often best, especially for fitness gains, to simply get more out of those 60 minutes than spend more time exercising - do intervals and push yourself and work HARD those 60 minutes. Make them count. :)
However, adding in some yoga and walking to your day in addition to a (tough?) 60 minute class is not excessive exercise. I would say if you are enjoying this routine, that's FINE! The only problem is if you feel that you HAVE to do that much exercise "or else I won't lose weight". No, that would be false. But if you just LIKE to do that much exercise, go ahead!
People who exercise more need to ensure they're fuelled more. You can't work out 2 hours a day on 1200 calories. :)
As long as someone is adequately fit for the amount of exercise they've chosen to do, appropriately fuelling themselves, and have a realistic approach to weight loss, there is no actual problem.
The problem is more like people who spend 3 hours a day in the gym sweating up at the cardio gear in the false belief they have to do this for some reason.
Deb, in New Zealand