I used to have the urge to let these types know they were wrong and explain why, but then I came to realize:
1) Their pathological need to act knowledgeable is due to insecurity.
2) My need to prove them wrong, was because it bothered me that they thought I knew less than them.
3) Those who speak the most and/or the loudest, often know the least, or are just repeating second-hand opinions.
In the process of transitioning, I've learnt to care less about what others think of me, and I no longer need to prove myself in the eyes of people who don't matter to me.
I now let them finish without interrupting, smile, say "thank you", then carry on with whatever I was doing.