Fructose is actually bad but that isn't the whole story. Fructose is only bad when consumed at a poor ratio relative to glucose. If you are eating 1:1 fructose/glucose, you can properly digest and use the energy from both. If you are too skewed towards fructose, it is less likely your small intestine will successfully digest the fructose, and it will make it to your large intestine and cause IBS, inflammation, hormonal disruption, etc. Reference low FODMAP diet and frustose malabsorbtion if you want to read into it.