This is quite a shocking statement.
You must know as a professional theat you absolutely DO have preconcieved ideas and bias. So do the families that you work with. It's normal and human to have these biases and isn't a deficiency.
BUT when you do research you confront, acknowledge and try to mitigate for bias, and where you can't mitigate then you report on how that effects the outcome of your research in terms of reliability and generalisability.
Otherwise you produce junk papers, waste scarce resources and let down those you suppose you are supporting. Very poor.
Even poorer potentially is the inclusion of low quality research in a systematic review where it can skew findings dramatically. Again you KNOW this because you say you carry out systematic reviews so you know about protocols and risk of bias assessment.
Trans people deserve better. Better research, better care. Do better.