>Should you be free to make (acknowledged) sub-optimal decisions for yourself that adversely affect others?
Yes, this is what personal freedom is about. Optimal-ness of decisions does not matter.
There are some things we agreed as a society are not only suboptimal, but harmful enough to warrant restricting some of that freedom. Note the enough, we hold freedom above (or at least used to hold it) some consequences that may result from its existance. Ideally this standard of enough should be pretty high.
The argument against censorship is that censoring what people discuss is harmful to both that freedpm (fundamental - according to how we base our society) and to society as a whole, seeding dissent from these groups that are singled out.
EDIT: I also think your assumption is wrong in that it is dubious if there are people whose opinion is better. Just look at science's history, where most of the (now recognized) big breakthroughs were first seen as absolute stupidity from the established experts.
>Anticipating the "no - if it's illegal" argument, how would that be the philosophically consistent with freedom to choose free from having a group of people who are "smarter and better" choose for you?
As for this, society is hardly philosophically consistent. At some point a concensus has to be reached. Here practicality forces us to abandon philosphical perfection in order to preserve social order.