This challenge will continue to be there. Those with a conventional mindset and followers of structured research process will have great difficulty appreciating participatory tools.
Please try to take them through a practical exercise and let them see for themselves the difference. Even after that, in case they do not appreciate participatory methods, please leave them to their fate.
trying to answer to your question I would say that:
1 - Participatory Action Research (PAR) has already a vast body of knowledge and empirical evidence that sustains the claims about its effectiveness, efficiency, scientific validity and overall benefits. So that could be a starting point;
2 - Further on, the real outcomes and impacts of PAR are better understood when directly experienced..so, inviting those researchers into the PAR process could work really well to your benefit.
3 - PAR is not necessarily to be used everywhere, always and for everyone..so double check if that feedback is not a necessary input to your process.