BELFAST, Maine — Some folks wonder why pharmacist Kevin Holland opened Belfast Drug Co. across the street from Walgreens, and only several hundred feet from Hannaford, which offers its own onsite pharmacy. “They say, ‘Are you crazy?’” he said. “But I don’t view them as competitors. I think what we do is different.” That difference is apparent as soon as a customer steps inside the new drug store, which opened last week in the Starrett Drive space formerly occupied by Bell the Cat coffee and sandwich shop.