I thought most blokes just ignored those remarks until they finally gave up and moved onto the next thing, like the lawns don't get mowed enough. So you need reasons.
1. There's seven days in a week, so your four bikes short.
2. KTM's are known to be unreliable so you need the third as a back up.
3. You suffer from OCD and can't help yourself, but three bikes are cheaper than ten years of therapy.