While I hate to say it, guests are under no obligation to be nice, friendly, or even a step above civil to you as their hosts. We all love it when they are friendly, warm and happy, but just because they aren't, isn't grounds to cancel them without penalty (which is what that "I don't feel comfortable" option is for, btw). You CAN cancel, but there are big penalties for doing so. If you feel that's your only option, you should take a good long look at if you are cut out to be hosts at all, because, trust me, being rude is only scratching the surface of what you will have to deal with regarding customer behavior in the future. Read some of the posts in these forums - it will get way more difficult than terse conversation, rolled eyes, and crossed arms. Just saying.... hosting on Airbnb is not for everyone.
That being said, take into consideration your own anxiety with being a new host. This is stressful stuff. You may be more sensitive at this moment because you want everything to go smoothly and perfect and, well, smart. It's hard when the guest is sort of ruining what you expected to be an easy thing to do. Take a deep breath and recognize that they don't want a crappy experience either and that they may just be having a rough day.
Good luck.