That's right. Because producers, including photoautotrophic and chemoautotrophic, are all organisms that can synthesize inorganic substances (CO2 and H2O) into organic substances, photoautotrophic will undoubtedly produce O2, while chemoautotrophic organisms (like nitrifying bacteria) use the energy released when some inorganic substances are oxidized to produce O2. Think about it. If you produce O2, but you are still anaerobic, how can you survive? That's not killing yourself by producing O2.