Thank you, Joelline.Possibly. It certainly means that I voiced no objections to your idea! The word "just" might suggest that the person wasn't actively supportive (but didn't say anything at all).
Hi, Ms Missy.Not really! What it means is that I suggest that we sneak into the movies without paying. You're hesitant at first, but I manage to talk you into it. We both get caught soon after entering the theater. By saying, "It was all your idea, I just went along with it" you're really saying that it's all my fault that we're now in trouble. You want to feel that you're not as guilty as I am, even though we both did the exact same thing!