Anywhere near you is either an intelligent articulate guy or a hard to take bore. If you feel you can't continue listening to the conversation please don't ruin your mood sacrificing yourself listening to what you don't like. Find a good excuse like going to the restroom or making a private phone call. But please take time to listen to the bore even for a maximum of 5 to 10 minutes for politeness sake. You don't have to hurt other people's feelings because you find them a bore. Your mood may not be set in for that type of discussion at that moment. Remember the bore now may not be a bore tomorrow so in any way that you can politely make an exit please do so.