I have supported aiding Ukraine in its fight against Russian aggression. I don’t understand conservatives who want America to watch Russia crush an independent country. That is not the America I thought conservatism embraced. At the same time, the opponents of aid to Ukraine do make valid points. For example, America should not seek regime change in Russia; peace should be pursued as vigorously as war; and compromises — such as an agreement that Ukraine does not apply for NATO membership, at least for a specified amount of time — will be necessary. But there is one argument made by...