It’s both. There is a very vocal contingent who insist that obesity is not unhealthy.
Every philosophy or movement has outliers that misinterpret and act outside of the bounds of that movement and we understand that those outliers don’t represent the group; yet people always look to those outliers with the fat acceptance movement — the fat acceptance movement is not given the benefit of the doubt like others are.
To me that implies that there is underlying bias.
From my vantage point the movement has largely been co-opted by extremists who want to pretend that obesity is not a health problem.