DH has a friend who is a teacher. A science teacher no less. This means she is the world authority on everything.
She decided to tell my DH that there were no phone deals for x amount with an iphone. Except DH actually got one. But nope she knew better.
She's pretty much like that on everything. Thing is, she has an education and its no better or worse than anyone else in our circle of friends; she's someone you would term intelligent, but I find her pretty thick actually. What she lacks is life experience, general knowledge and common sense. And the ability to respect what anyone else knows or thinks.
I've had better conservations with people who I would term "less intelligent" because they are interested or have a great deal more about them in other ways. I tend to find that conversations have to be two way processes or they get a bit dull really.
Intelligence has got nothing to do with the topics of conversation I have. You can have plenty of interesting conversations with 'less intelligent' people. Not to mention some 'intelligent' people are just incredibly dull.
Conversations usually are about around things you have in common or something that just comes up naturally. I certainly wouldn't start a serious conversation out the blue on a very serious subject, just for the hell of it. I wouldn't moderate what I say around other people, because that would be patronising and I wouldn't be being me. If they don't get it, they don't get it and the conversation just ends naturally. No point in persuing it, but equally someone might show interest in finding out what you know. I tend to find respect for the other person comes into the equation somewhere too - something that also has no bearing on anyone's intelligence.
If you listen to others you might find out something you didn't know or see things from a perseptive you might not have thought of. Even if something isn't as intelligent as you are used to. Their point of view is still worth taking on board for various reasons.