He says we don't have to taste poison to know that it's bad. His 'logic' is that apostates have nothing to say but poison > therefore, what they say doesn't have to be tested and can be rejected outright without listening and testing first.
Why is it that most of us have some sort of poison sitting on our shelves in the first place? It all serves a useful purpose, if used properly. It's not there to be consumed but when used for its intended purpose. it can prove to be very beneficial. Without it, we could end up with serious consequences.
With the Covid virus, you can find bottles of disinfectant's everywhere. It kills most harmful bacteria and it's considered extremely useful. But it's a poison, it's not meant to be taken.
If Splane really wants to describe apostates as poison then it could also be viewed as being beneficial to JWs in helping cleanse the falsehoods that they are trying to spread.