The temptation is to condemn, to tell the person off, or to make it clear that this is not an acceptable way to behave. This may, indeed, be the best way forward in the situation. However, it may not. We have to take great care of the spirit in which we act - and the way this may be experienced by other people. We need to be ready to listen and ask questions.
Nothing is served by arbitrarily closing down conversation.
We may feel better or 'cleaner' for having avoided an uncomfortable or objectionable topic, but in doing so we may well have abdicated our responsibilities as educators. Where it is necessary to make our position clear we need to address the act or opinion rather than attack the person. This leads us to something else that we need to take to heart as informal educators. In the work there is a lot of talk of 'getting inside the other person', of empathizing. At first sight the wish to see things as others do, to 'step into their shoes', seems reasonable.