Because it has this prejudice that Republicans and only Republicans should select its candidates, the Republican Party has a preference for conventions. However, not all who call themselves Republican feel the need to exclude those who are not Republicans, and so these folks do not like conventions. Sometimes they find the strangest reasons to be against conventions.
Not Too Conservative Too Conservative is always good for a laugh. Check this one out.

You’re so humorless. That was not meant as a major reason to cancel the convention. It was simply a topic being bandied about, primarily by seniors for whom attending an all day convention is tough enough as it is.
Humorless? Darn! And I thought it was funny.