Again, the leadership of the Seventh-day Adventist church has the biblical authority and historical precedent to designate an official structure to collect and distribute the tithe and any argument against this is an argument against the God ordained authority of the church. Refusal to honor the structure is a refusal to honor this authority.
In one sense, the Bible & EGW are irrelevant, when you join any organization and promise to support it with a percentage of your income (%3, %10 tithe, %40, etc.) then you must do this or you are dishonest, it's that simple. If you join the National Rugby Team of Fiji Fan Club and promise to pay your dues and then later refuse then you are being dishonest. If you do not like or approve of the actions or teachings of the leaders in the National Rugby Team of Fiji Fan Club then you can seek to bring change as a member and continue to pay your dues or you can just leave the club. It's that simple.