I put the CSS code .ai1ec-time.ai1ec-row {display:none !important;}
in the Themer Singular template that I use to display all the Events, so that solves the immediate problem. But to make this work I had to make 2 Themer templates, one applied to Events with category = repeating and one that excludes category = repeating (without the css in the template)
Still it would be great if MB had a CSS "field" that could insert custom CSS onto a page to style elements based on MB conditional logic.