No I do not agree.
1)There is no requirement in the NPPF to support equestrianism.
2) The policy you are proposing does not include any mention of the loss of agricultural land (see DEC2 (ii)). RDC does have an obligation through the NPPF and Core Strategy Policies to protect and promote agriculture, therefore this policy would appear to be against both national and your own existing policies.
3) This policy appears to be designed for people moving into the area and promote the leisure activities of possibly one or two people if that household above the general enjoyment of the countryside and its proper use in food production.
4) It does not tackle the problem that fields associated with the property will also be lost to agricultural production - is a change of use required from agricultural to leisure? Has any analysis been done as to how much land is lost to agriculture in this way? A loss will occur with each application approved.
As a partner is a small agricultural business which, unfortunately due to the lack of small farms or small holdings available in the area, we are reliant of the houses with 1 or 2 fields attached to provide the necessary ground for our animals to graze. If any of these properties change ownership, and this policy is in place, then we may easily loose the grazing and be forced out of business.

5) The current standards laid down by DEFRA for farmers to follow will not apply and therefore these areas will not be looked after in the same careful manner, detracting from the views of the area. We do live in an AONB.

6) This will fuel the housing prices for properties with land attached, taking then even further out of the reach of anyone local to buy.