Nothing wrong with shoulder charges, but players need to know if they get them wrong and contact the head then they get put on report. If you choose to employ a tackling method because it provides maximum impact, then you must accept the inherent risk of reduced control you have when using that method.
You can't plead "accident" or "unintentional" contact as a defence IMO. They have careless and reckless gradings for a reason, shoulder charges fall in that category. I feel the same with head clashes as a result of shoulder charges, should be put on report as well.