So, have them speak in Sunday school ~ we think you guys are in error however, and there’s plenty of scripture to back us up.
(This doesn't seem to follow. Are you supporting women speaking, teaching and preaching in the assembly? I thought you were arguing for the proposition. I will continue in that vain.)
The Bible does not contradict itself. (It cannot be both A and ~A). For a woman to speak in the assembly and to preach/teach with authority over adult males is in direct violation of the doctrines of 1 Timothy 2 (and 1 Corinthians 14). A church/assembly of believers that permits this shows ignorance and/or blatant disregard for the clear teachings of scripture. (e.g. Twisting [diakonon] to mean women can violate prohibitions against speaking/preaching/teaching).
For though we walk in the flesh, we do not war after the flesh: 4 (For the weapons of our warfare are not carnal, but mighty through God to the pulling down of strong holds;) 5 Casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ. (2 Corinthians 10:3-5)
It is a "high thing that exalteth itself against the knowledge of God".