Denying the rest of scripture in support of doctrine derived from speculation regarding the mechanics of sinless conception led to the logical necessity of yet another sinless conception, but not requiring a sinless mother, otherwise it’s turtles all the way down with an entire line if sinless women all the wat back to Eve, a logical contradiction even further astray from scripture.
Or, maybe Mary wasn’t sinless, yet conceived a sinless child, herself, rather than her mother doing so as you believe?
We’re not denying the rest of scripture. We’re keeping it in context.