That negative score is added to the positive score from the expertise part of the author when I determine how much credence to give their argument.
When presented with a true argument, information that can be reasoned about or verified, this is where penalization is not appropriate - healthy skepticism ensures you are critical of it, but an attitude of penalization adds a handicap to every argument produced by a committed person regardless of any truth it could hold.
When the argument is almost entirely emotional however I'm inclined to agree - a negative weighting is reasonable.
The parent's principle is in fact quite applicable in this case due to the lack of arguments presented along side facts and explanation, but that does not justify over generalizing it to argument from all committed people.
This feels like an unfairly broad brush to paint committed people with. True commitment and expertise invariably results in truths indistinguishable from opinion to the outsider, they can offer considerable insight to those who will listen.
> When weighing people's opinions, expertise should be rewarded but commitment should be penalized.
"Penalized" is too dismissive, and borderline bulverism. I would say it is important to listen to the committed while being critical and wary of any bias they may have.