I think the argument that June is "not fast" and therefore this discussion should not be considered is very flawed. Sport is amazing because it provides an opportunity for people to commit long term to a passion and see themselves grow with the end goal of making varisty, competing in college, winning and NCAA title and going to the olympics. Just because June is not a threat for an NCAA title or Oly team spot does not mean her choice to participate does not disadvantage others.
The logic of any good argument should always hold in another framework. What if a 10th place conference finisher undertook an action that artificially caused them to have more muscle density(i.e. HGH) and moved up to a 3rd place finisher. Not really a threat in the big scheme of things but this community would be outraged.
There is a girl who would be the team leader, regional qualifier etc who would grow tremendously if the true spirit of sport were followed. I respect that June is a person and should be treated with kindness. So is the individual who is at a competitive disadvantage for team lead, school records, rankings etc. and they are being harmed by transgender athletes' choice to participate.
As a final note consider the similar situation of Ryan Hill. I believe he was required to take testosterone for a time and felt it would put other athletes at a disadvantage if he competed so he sat the bench for some time. If transgender athletes feel strongly enough about the need to transition then they should be okay that certain avenues like competing in womens sports may not be open to them.