Apparently someone should tell them that being transgender has zero implications regarding as to whether or not someone will be a good or bad parent.
But, someone should remind them, in order to maintain a consistent mentality, that priests, as a whole, aren't exactly known for their good treatment of children, and the Church should probably stress parental caution when leaving their children alone with a priest. Maybe priests shouldn't be allowed to be god parents.
It seems like a number of people are misunderstanding what a godparent in the Catholic church is. I don't know what other denominations mean by the term, but years (ok, a couple of decades) ago I have been a godparent a few times. I would no longer consent to be one, nor would I qualify.
The purpose of the position of "godparent" is as an instructional position according to, and regarding, the teachings of the Catholic church.
It is meant for the person (sometimes called a sponsor, for older converts) to be involved in the spiritual/religious education of the child/convert. It does not involve physical care of a child, and isn't really at all like being a parent.
Generally, godparents don't do much, but in the event of the death of the child's parents, the godparent is agreeing to see to it the child is instructed according to Catholic teachings.
For that reason, there are certain requirements, and among those requirements are some stipulations (this is just a general explanation) that if the person is not living according to the teachings of the Catholic church, the person is not to be a godparent. I think the church assumes that a person who does not consent to the church being an authority on spiritual/religious matters in their own life, and does not live according to the teachings of the Church, that person would not really be inclined to ensure the instruction of someone else in those teachings.
In my recollection, and understanding, I think there is also the reason, (possibly a main reason) that in order to be godparent, or sponsor, it is necessary that one have previously been Baptized and Confirmed in the Catholic church -- because they are
fulfilling a role from the church. The godparent is an important part of the sacrament of baptism, and is in effect, being considered as an arm of the church. So, it is more of an a representative of the church in this particular instance, than anything else.
I understand why this sounds unkind and unloving. In a way, I see it that way. It was due to matters similar to this that seemed to me to unloving to people for being who they are that caused me to leave, and no longer consent to be under the authority of the church. However, at the same time, it makes sense to me that a religion would not give a position (as teacher) to a person not living according to its teachings.
edit: This might help some that aren't familiar with it:
http://www.catholiceducation.org/en/culture/catholic-contributions/the-role-of-godparents.html