Sttrrrrrange things happen in our world. The laws of the "three weeks" [בין המצרים] are based on mere custom, yet people follow them meticulously. You see a lot of unshaven faces, the music goes off, weddings are postponed etc. etc. But why do we have these customs of mourning? Because the Beis Hamikdash was destroyed. Why was the Beis Hamikdash destroyed? Sinas Chinam.
But the Sinas Chinam continues on unabated. Siblings don't speak. Cousins plan not to invite each other to upcoming simchas. Former business partners continue their litigation in court against each other. Atterneys are very busy working out divoroce settlements and the list goes on and on. So Sinas Chinam and Machlokes, Torah prohibitions, continue with no reduction in strength or intensity, but to remind ourselves not to have sinas chinam and machlokes, we follow the custom not to shave for three weeks. It is like a diabetic wears a bracelet to remind himself not to eat dangerous foods and as he stares at his bracelet he downs a whole box of sugary cookies. Silly-silly!
I am not recommending that people shave. I personally haven't shaved in well over 20 years and even when I did, it only happened a few times. I am in favor of beards, if possible [although women are exempt - on this one I don't hear any protests:-)]. CERTAINLY during the three weeks one shouldn't shave. No question!! מנהג ישראל תורה! We take minhagim seriously. [That is why this whole internet campaign to allow Ashkenazim to eat kitniyos is incorrect]. But we must have some proportion. Shaving is to Halacha, like the flu is to health. Sinas chinam and machlokes are CANCERS.
So instead of just talking about it - let us actually uproot the sinas chinam and machlokes from our midst.