Non-Muslims ask: "Why do Muslims keep beards?

Answer

Tell the non-Muslim that you don't know because you are not a person of knowledge. Refer such persons to the Ulama. Furthermore, it is futile to attempt to explain to non-Muslims why Muslims keep beards. Such an attempt is unprincipled since they do not accept the Usool of the Deen. It therefore will be a waste of time and a redundant exercise to explain a furoo' mas'alah to them. It is not going to convince them to accept Islam. On such issues give them an Ilzaami response. Ask the non-Muslim: Why do you shave your beard? Whatever will be his answer should be your response. There are a couple of small booklets written by the Akaabireen on this issue. The wisdoms are explained in these booklets. Study the booklets.