I used to think that being "opinionated" carried a negative connotation. But I know so many people who never have an opinion. I don't just mean they don't share their opinion. I mean, they just don't have one. They don't care. I totally expect that from someone in middle school or high school. But by the time you reach adulthood I would think you would have had enough life experience to be able to formulate opinions on certain issues.
How are you even close to being qualified to vote if you have no opinions on the major issues in politics? How can you tell your kids to abstain from drugs/sex if you have no opinion on the matter or "don't really care" what teenagers are doing these days? How could you ever serve on a jury (which is part of our duty as a U.S. citizen) if you think that the way others live their lives doesn't affect you?
I don't share my opinions because I want to change anyone's mind (well, not always, haha). I mostly share my opinions so people know who I am, what I believe in, what I'm about. I think it's most important for parents to share their beliefs and opinions with their children. Kids are sponges. They will soak up ANYTHING and EVERYTHING they are taught. It doesn't mean they will always believe what they are taught, but it will be their first beliefs and the foundation to their lives. If you are a conservative Christian do you really want your child learning about our creation from their science teacher who is going to teach about evolution? If you are against teen pregnancy/abortion do you want your child being taught about sex in school (elementary to be exact) before you ever talk to them about it?
To me, having an opinion is knowing who you are. It's not being afraid to stand up for what you believe in. It's confidence. It's knowledge. It's a huge tool for parenting.