Gesundheit!

Once while the Blessed One was expounding the Dhamma, surrounded by a large number of bhikkhus, he sneezed. The bhikkhus made a loud noise, saying: "Long life to you, Lord; long life to you, Lord." The noise interrupted the talk on the Dhamma. Then the Blessed One addressed the bhikkhus thus: "Bhikkhus, when 'Long life to you' is said to someone who sneezes, may he live or die because of that?"

"No, Lord."

"Bhikkhus, 'Long life to you' is not to be said to someone who sneezes; whoever does so commits an offence of wrongdoing."

So then, when bhikkhus sneezed and householders said "Long life to you, Lord," they were embarrassed and did not answer. People disapproved, and they murmured and protested: "How can these monks, these sons of the Sakyans, not answer when 'Long life to you' is said to them?"

Bhikkhus told this to the Blessed One. He said: "Bhikkhus, householders are accustomed to such superstitions. I allow you, when they say 'Long life to you,' to reply 'May you live long.'"
—Cullavagga 5:33, as retold by Ven. Nanamoli

Habits are hard to break. Social conventions are hard to change. Long-held assumptions linger beneath the surface, unexamined, rolling along just as so many things tend to do in this samsara.

This passage from the Vinaya collection suggests that an appropriate response is one that does not hinder Dhamma understanding. Out of compassion and wisdom, the Buddha advised the monks to speak with these householders in the customary way.

In those unguarded moments when a person speaks or writes from his or her perspective of past experiences and habits, we need to be careful before we turn things into a confrontation of beliefs. There is a proper time and place and manner of speaking and interacting with others. In the Abhayarajakumara Sutta, the Buddha explains the characteristics of wise speech in more detail.

When we talk about the Dhamma with another person, we need to exercise this type of caution, particularly if there is the potential for bitter disagreement. We might think that we are right, and we might think that the other person is wrong, but what is the proper time to bring things to a head? Particularly in print, or on the Internet, where our words linger and are seen by many different people at many different times, we will do well to consider before we write: What will be the likely effect of my words? This starts with understanding. In my opinion, if we do not first listen and understand what the other person is saying, then we cannot know whether the Dhamma words we offer are beneficial.

Be gentle.