Transgender bathroom use and statistical perspective.
There have been bathroom access laws for trans people in various jurisdictions world wide for around 35 years. In 35 years there has been ONE confirmable case of someone abusing access to commit sexual assault. In the past five years at least five Americans have been shot by dogs--no joke, google it. Extrapolated at the same rate that would be 35 people shot by dogs over 35 years. So your hypothetical 8 year old is 35 times more likely to be shot by a dog than he or she is to be sexually assaulted by a trans person in a public restroom.
Guns don't kill people, dogs with guns kill people.