You need knowledge to decide whether something is good or not, when the policy is fact-based. You dont need knowledge to decide whether you _want_ something or not, when the policy is purely opinion and preference based, for example filesharing. You dont need domain knowledge to decide that for you freedom to share information trumps the freedom to profit off information creation by enforcing artificial scarcity.
> the ordinary person will vote for the person who promises
If people are not allowed to make bad decisions, you dont have democracy, but a kind of dictatorship disguising itself as democracy. "You can vote on whatever you want as long as I and the few other stakeholders approve of the results" is a fake democracy, designed solely to sedate people's natural desire for co-participation and to prevent uprising.
Whatever your justification, you're trying to ban people from contributing their small share to the overall policy because you dont like their likely policy. One of the primary goals of the pirate parties is to fight opinions like yours and people like you by enabling maximum participation for everybody. Direct democracy baby. Bring on the regular swiss-style referendums.