why should that be the case? Nobody has suggested that the thread was offensive or that it brought anyone into disrepute - perhaps you're jumping to all kinds of conclusions without hitting the right one?
The thread was deleted because part of our editorial policy is that we don't ask why a certain person isn't posting any more. There can be a thousand reasons why someone decides to leave us or take a break for a while, and it's none of our business - they have a right to privacy in that respect.
Many people stop posting for one reason or another, but that doesn't necessarily mean they aren't still with us - I can see quite a few people who were once regular posters logging in and out quite regularly, they just choose to remain silent.
We're not going to change our policy on this - it's done to protect peoples' right to come and go without having to give a reason.