It shows how you feel of their opinion and sheds doubt on your interpretation of the situation. And also sways the listener to your opinion. It's best to share facts without the emotion.
TIL doing a pattern of capital and lowercase letters means you're doing a dumb voice. Didn't know that until looking at the replies, now I feel like I have a lot of stuff to change on my countless profiles.
To answer the question, I don't think so. I don't use the dumb voice just for people who disagree with me, it would have to actually be dumb, like the teacher who thought special ed gym class was better for me because that's where people go who aren't social enough with their classmates (and then you get to the class and wonder what the logic is because you solved a people problem by subtracting the people).
What is your goal? To debate (convince) or to humiliate them?
If you do it in real life in a debate with your adult friends, you will be seen as a failure. It's immature and speaks more of your weaknesses. Because you're actively mocking the person, as opposed to attempting to have a conversation.
Doing it in real life to mock someone is acceptable. You're not having a debate or conversation. Your goal is to insult them.
Context is always important. Everyone is entitled to an opinion, and doing this is a good way to express your opinion about someone else's opinion. Just remember, it's easy to sound like an insufferable twat when done poorly.
To be fair, if emotion isn't involved, that's basically just a sign of indifference. You owe it to yourself and your "opponent" to actually care about whatever it is you're discussing. What truly matters is understanding and prioritizing the why behind your feelings and honoring that, regardless of whatever random impulse those feelings are currently bringing about.
My inner monologue does lots of voices. It does a great Christopher Walken. It also does a good Bill Cosby, especially when talking about pudding. I get offended when it uses Cosby's voice because he's no longer acceptable in society. My inner dialogue can't keep up with changing times. It's still saying "Where's the beef".
It depends on how stupid the idea is and whether the originator of said idea should be expected to know better.
For example, at my employer there was a senior engineer that made the FEA engineer waste a month trying to fix a design that would never work, simply because senior engineer wouldn't spend 2 minutes drawing a free body diagram. That level of stupidity is deserving of mockery