From former emails and postings - a cricketer!

But seriously, it would make you a non-conformist at a public school and a Saturday shopper during the five(six)-nations during winter.

The best I can think of would be a form of anti- or contra-. Rugby is an Etymological word (please correct me!) and is named after the place from whence it began - like cheddar, Gorgonzola, champagne etc. so it is difficult to give it a handle. Anti-Rugbyist, contra-rugbyite just don't roll off the tongue as well as CRICKETER! so maybe the form should follow what you are a fanatic of and not what you aren't. Example: 'Do you like Rugby?' 'Hell, no. I'm a die-hard cricketer'. Nuff sed. Do you really need to be so ardently anti-rugby (or anything else) to have a new word (or prefix/suffix) coined for the purpose??