'My dad can kick your dad's ass' type arguments works for some things but it does nothing to extend an intellectual discussion regarding whether or not evolution does the best (or the worse) job of explaining the biological world.
Credentials, real or imagined also are not the issue at hand.
The issue at hand is; what scientifically sound principles can be brought to bear on the question of how different species came into being.
What common ground can be agreed on by all? What about; genotype determines phenotype. That is to say, that what makes a wombat different from a chicken is the content, arrangement, structure of its genomic DNA. If that point cannot be agreed on, then no intellectual discussion is possible. It is a required first principle.
If anyone would like to argue that wombats have always been wombats since genesis, what is the evidence? Something to consider is, to take that position is to also take the position that genomic DNA (or RNA in some cases) of every and all life forms has been more or less completely stable since genesis. That is to say, that unless the critter went extinct, the genomic DNA(or RNA)was the same in the beginning as it is now.
