It seems you have a chip on your shoulder. The yard is not trying to dictate - someone (you won't name who) has in some context said they think horses should only need to be ridden in a way that doesn't chime with yours. Where is the dictation, where is the issue?
We all know it is dependent on the horse, the rider, the work etc. Ultimately it is up to the rider, however if someone knowledgeable makes a suggestion then I would always question myself.
I have known people discuss, suggest more or less riding. I listen to them more or less depending on how much I respect their opinion.
OP if you respect their opinion have a chat and find out why they are suggesting it. IF this is them generically saying all horses should be riddne 4 times a week ignore them and move on.
Agree with the above, we can hardly offer advice if we aren't being given the relevant information needed. As has also been said, I don't think anyone is dictating to you, as no one has the authority to whilst you're on DIY. You're not being made to do it, so not really being dictated to.
That's my thought I don't seen an issue with anyone asking someone why they ride their horse 6 days a week, which is what the OP said happened, it's not an invalid question and an easy one to answer for most people, issue resolved.
That is not the same as saying you must only ride your horse 4 days a week, which would be dictating.
OP it sounds like this yard doesn't suit you given your other thread too, have you thought about moving?
There isnt any possibility someone is riding the horse when you arent around and therefore wanting you to ride it less? Presume not but it sometimes happens.
The thing about livery yards is that generally people will always have an opinion.
But it's whether those opinions are voiced in the first place (generally, I don't voice opinions, even if asked, unless it's an immediate & real threat to the horse's welfare). If an opinion is given, then consider if by someone with good stable management standards themselves and puts their horse first or if it's someone I wouldn't take advice from in a month of Sunday's.
If it's the first, then I'd review my management for area's in relation to the concerns highlighted. I'd do some research & have a chat with my trainer (she's my 'go-to' as really does put the horse first) & other professionals involved if need be.
If the last, then just politely thank them in a round-about non-comittal way & continue as I was I'm not friendly enough with 99% of people on my yard for them to know fully what or why I do what I do with my boy and vice versa.