Not offensive, and not a violation if the question requires a yes or no answer.
Some askers get annoyed at more than a yes or no answer to their Poll questions.
If the asker wants to know the reasons for yes or no answers, they'll ask for it, with the addendum why or why not, which then changes the question from a simple fun Poll to a privacy intrusive Survey.
The appeal reviewers of customer care are Zombies, chained to their cubicles with only one button to generate random appeal decisions and responses. They work cheap - just feed them the rare newbie that acts like they actually care.
We can see some of the people answering here are showing signs of the Zombie virus, cackling away with their scripted answers like a pandemonium of parroting puritans.
Old rule..... "Yes" or "no" answers are OK, but only if the question calls for a "yes" or "no" answer.
Yahoo Answers Team Blog Entry.... "Is it OK to just answer with a yes or no? Yes. If it makes sense in the context of the question, that is."