Often I ask them a counter question, especially if they are trying to get me to answer in a way which isn't beneficial. At these times often what others try to do is put the spotlight on you, put you on the defensive. So I try to be very skilful at asking a counter question, and putting the spotlight back onto them. For example, there was a situation, a difficult one, I was witness to it. Someone was wanting Steve's praise. They had brought their girlfriend to a retreat, and wanted Steve to tell him what he thought of her. Now Steve's pretty skilful in those situations. The fellow came very excitedly to Steve and asked, "What do you think of her?" Steve answered, "Isn't it more important what you think of her?" Now that's a good counter question.
Our truthfulness needs to be linked with lovingkindness. And our intention has to be based in compassion. There are times, though, depending on the situation, where we may answer truthfully, yet it hurts the other person's feelings, if we see it is out compassion for them. Sometimes Steve and myself have been put in this position, which is rather uncomfortable. But depending on who it is, if they're open, we may be able to say a truthful answer, which doesn't feel good.
So it really depends on the situation, whether you answer truthfully, or whether you ask a counter question. If the person is just trying to bait you, usually either silence or asking a counter question or changing the subject are your best choices. If it's people who don't meditate and understand their mind, then their normal mind is usually going from one subject to another anyhow, so often they don't even notice if you change the subject. And besides, it's quite okay, especially if you ask them something interesting about their life. Most people like talking about themselves. And then you get out of the spotlight. And they might go on for hours!
So it depends on the situation whether you say something truthful or say nothing or simply change the subject. The Buddha was once asked the question "Would the Buddha say things that are unpleasing and disagreeable to others?" And he answered that there is no outright yes-or-no answer to that question, it depends on the situation. If it's out of compassion, I'll often say things that are displeasing and disagreeable to others. We can't always please people with our answers. But if we see that it may not be very skillful to answer in these ways, changing the subject or asking a counter-question is better. Trying to use truthfulness with compassion and lovingkindness needs quite a bit of wisdom to know how to get ourselves out of these situations.