I decided to send Pastor Fisk a question on his contact page, to see if he might address it on a future show. The upper limit was 500 characters, so I had to really slice and slice to get it under the limit, but I'm decently happy with what I was able to send:
To say "adult baptism is God’s work" is nothing less than special pleading. Why can’t I assign the label “not my work; God's work” to other things? By this principle, I could consistently be a tithing-circumcisional-abstentional-regenerationist and still profess that I hold to sola fide. Please tell me why I'm wrong. If your answer includes 1 Peter 3:21 or Romans 6, please prove that those are definitely not Holy Spirit baptism (Matt 3) but are definitely water baptism.