OK - here's my tuppenceworth (as a fellow sufferer of chafing, although mine in Crohn's induced).
1. Make sure that you have properly fitting shorts. As Mr Hummers says, choose the shorts for the conditions.
2. Make sure that you use a non-biological washing powder/liquid when washing your shorts and make sure they are properly rinsed. Wherever possible air dry them outside. Make sure they are completely dry before putting them on.
3. Have a shower before going for a ride. Make sure your undercarriage is dry and then use a light moisturising/barrier cream - I'd recommend
Udderly Smooth or similar. Avoid using a heavy cream, such as Sudocrem or Vaseline. These will block the pores of your skin and make things worse.
4. If you feel yourself getting sweaty during a ride, take the chance at a tea stop to nip into the loo, have a quick wash with plain soap and water, dry carefully (pat dry - don't rub) and reapply some of the light cream. Do NOT use alcohol based wipes - this will dry the skin out and make things worse. If you are already getting a bit red downstairs, then putting alcohol on it will make it worse.
5. If you're riding on a particularly hot day, take along a spare pair of pants and change during the ride.
6. When you get home from the ride, take a shower and make sure that you wash well. Use a mild soap and rinse well. Slip on a pair of loose cotton boxer shorts and let air circulate.
Having had a good look at the photo (for purely scientific reasons), does sir shave? If so, leave off for a while and then get a back, sack and crack. Less irritation will result.
The only other thing I would ask is whether you also get these problems when not cycling? If so, it may be worth having a word with your GP, as soreness in the perineum area can be an indication of gastric/bowel problems.