Someone having done it doesn't make it a good idea. I'm sure you're aware of that. The point is it could weaken the frame. There's nothing wrong with breaking an old frame in and of itself. There is something wrong (very wrong) with breaking an old frame while you're riding it. A break could/would come whenever you stressed the frame adequately, and this is precisely the worst time to have it happen, since parts of the rider are likely to break as well. If you've never had the experience of having your bike give way beneath you under stress, then good for you, and you should strive to keep it that way.

Even if the tone seems a little harsh, people are trying to help you out. Also, you asked. Check in the framebuilder forum if you want a second (and better informed) opinion. Otherwise, take your offended reactions elsewhere.