Not really a valid argument.
There has been an ongoing bravado shown in regards to Taildraggers for many years. The best pilots in my opinion although they may give a friendly ribbing know, based upon sense (that is not so common today and never really was it seems), that this argument is really out of date and based upon Ego rather than facts.
Regarding sailplane pilots... Facts are facts... and the ability to truly and intimately know the medium we fly in can not be underestimated IMO. Not saying all Sailplane Pilots are better than Power Pilots, just as not all Tailwheel Pilots are better than Tri-gear Pilots... but you surely would become a better all round Pilot with experience in all of the above.