The inappropriate use of the “vexatious customer” process - not at all uncommon but a well trodden path for the avoidance of Openness, Honesty, Integrity, Accountability etc…
Whereas there “may” be genuine occasions of inappropriate, persistent or malicious contact and/or action, I’d suggest it is genuinely rare and easily managed.
What seems to happen however, is that ANY form of critical analysis of PC performance, even when measured against published statutory or ‘good practice’ metrics, is treated (by the PC and/or staff) as malicious, vexatious etc and the person that raised (often) legitimate questions is then “black-listed” from any further contact. What a gold-plated means of suppressing public scrutiny and accountability.
Such circumstances are actually facilitated (in the first instance) by community apathy - nobody really cares about the PC. This allows the repeated return of uncontested candidates, often over successive election cycles, and ‘cements’ in place the people and processes that have become normalised through the lack of scrutiny.
Because the incumbents have been in post, often for extended periods, they come to ‘believe’ they are there because they somehow ‘deserve’ to be rather than because they have been elected to be.
Add to this (which may or may not be the case) a clerk that is ‘happy’ with the status quo and an easy life with malleable councillors and the seeds are sown.
As if that wasn’t enough, you then have specific guidelines - as often as not promoted by local authority and county association of local councils - to “black-list” anyone that asks an ‘inconvenient’ question.
It is the perfect cycle of suppression of openness and honesty.
All that said, and it is worth noting that you are still only at the very start of your journey where there are many more mechanisms the PC can bring to bear to try and stop you continuing if they so decide, the actual question was about data protection.
If you have provided an email address to the PC as a point of contact, then they may use it. Until you notify the PC that you do not wish to be contacted by email and specify exactly what electronic data they may hold about you and how they may use it - they are free to use what you have provided to them for that purpose.
Don’t give in and don’t give up! There are plenty of mechanisms for publishing PC incompetence and bringing it to a wider audience. They can’t stop you audio/video recording meetings and then providing commentary after the event.