I think the following should just be generally understood and put this issue to some sort of a rest.....of course common sense dictates this shouldn't even have to be brought up, and someone's still gonna cry wolf so it'll never be at rest.
If you don't want to trade or send seed, then don't. But be polite about why and be non-judgemental....Golden Rule.
If you want to request seed from someone...
Try to contact them in advance if possible, which isn't always easy but make a try.
Ask "please".
If you have ANY seed, offer to trade first.
Be polite.
Don't directly or indirectly promise *any* action that you may, or may not, take with said seed unless you mean it....stuff happens.
If you don't believe in the practice, fine. But leave others alone about it...there is a "Seed Exchange" message board for a reason, whether you agree with it or not.