The high value you place on freedom may be because, in the past, freedom has tended to lead to pleasure. The idea that people are better suited to choosing how to obtain their pleasure makes sense to us now, because people usually know how best to achieve their own subjective pleasure, whereas forced pleasures often aren't that great. But by the time wireheading technology comes around, we'll probably know enough about neurology and psychology that such problems no longer exist, and a computer could well be trusted to tell you what you would most enjoy more accurately than your own expectations could.

I agree with the intuition that most people value freedom, and so would prefer a free pleasure over a forced one if the amount of pleasure was the same. But I think that it's a situational intuition, that may not hold in the future. (And is a value really a value if it's situational?)