Wow! I'm sorry but that trainer sounds like a jerk; and his/her attitude is the reason why so many people get turned off by the gym. Don't let what they said get at you.
There are lots of different ways to do things "right". You just have to find what works for you, which sounds like you did. Be confident in that!
It's my opinion that whether you do cardio, weight training, or a combination of both, anything you do that is more than what you did before is infinitely better than sitting on the couch or doing nothing! For example, I've lost weight by making simple changes: eating more veggies and fruits, drinking all my water, being committed to taking the dog on a long brisk walk almost every day and martial arts 2 times a week, mixing in the occasional exercise video or xbox game workout. I know that eventually I can and will do more, when I decide I'm ready and when I decide what I would really like to pursue, but for right now that's working and I couldn't be more happy.
It's not about how many times you fall, but how many times you get back up again!!!! You did it before, you can do it again! Pick yourself up, dust yourself off, and don't let naysayers thwart you from what works for YOU!