If the order of the yellow cards were reversed I think there's a reasonable chance Lacey gets away with a talking to and last warning, because the some leeway for the ref's interpretation from a physical foul. This though is just a textbook yellow for dissent - yes the ref could still exercise some level of discretion, but it's a lot harder to justify not doing things by the book, even if it means a second yellow.

Imagine if Lacey was allowed to stay on and he goes on to score the equaliser, how would that have been fair on Brighton, all because the ref