Can we call an objection to this?

In school we are doing a mock trial on whether or not Hiroshima was necessary. I am on the prosecution side so my job is to say that it was not. While researching I realized the prosecution side could bring up that the dropping wasok after the crimes the Jaanese had comitted on all of their Prisoners during WW2. Since this is a caseonHIroshima not WW2 crimes can we call an objection on this. As being irrelevant??? If not is there something else we cancall on them?? Thx.