I can understand an objection to taxing PPR disposals, on the basis that it might have an adverse effect on the property market and exacerbate a housing crisis - I'd like to see that objection fleshed out however, as the specific events (or decisions) that would have this effect are not clear to me.
I don't believe there should be any sacred cows when it comes to taxation, and at the moment the PPR seems to be a sacred cow. By sacred cow, I mean something that is exempt from taxation because that's the way it's always been or because it's considered politically unpalatable to curtail the exemption. The alternative to a sacred cow being a good old fashioned productive cow, which in this context is a tax exemption which serves to achieve a clear policy objective of the successive governments that continue the exemption.
It's not clear to me that a blanket exemption such as currently exists, is in the best interests of society as a whole. I see no good reason why a person (particularly someone who has benefitted from one of the many forms of tax relief or subsidies that have existed down through the years), who is actually realising the gain in the value of their PPR, shouldn't have the potential to be taxed on it.
To be clear, I'm not saying that ALL the gain should be taxed, and I'm not saying that the CGT rate should necessarily be the same as applies to most assets. I'm simply saying I'd like to see a convincing argument as to what principle it is that causes people to so strongly oppose the suggestion of any taxation on any gain.