Is using past participle instead of present one more polite?

On christianity.stackexchange.com I asked this question:

"Is it true that John Paul the Second restored the practice of selling indulgences in 2000?"

and one supporter suggested that I replace selling with sold as in this way it will sound less accusatory.

While not being a native English speaker and at the same not doubting a bit about that supporter's command of English, I am still puzzled here about how changing the tense of the verb can make things sound less accusatory. In fact, I don't quite see how the question is accusatory in the first place. Perhaps, there is some subtlety in English grammar here that I am not aware about.

Can anyone, please, explain this to me?

I posted as much in a comment, but on reflection I think it should be presented as a voteable answer, since differing opinions are being expressed.

Personally, I don't find sold indulgences seriously "awkward". It's a somewhat less common form, but to my ear it implies the speaker/writer is actually more precise than the average person who might have just used selling, and has chosen his words with great care. Similar usages include...

1: The proceeds of indulgences, first in the form of vow redemption payments and later in that of sold indulgences, were undoubtedly more substantial.
2: There is an ongoing practice of exchanged visits between the Fez families and their African friends.
3: They also demanded that the practice of unpaid labour for the chief be-scrapped.
4: The Panama Canal would not call for any change in our policy of untaxed navigation.
5: ...the devastating effects of the policy of banned abortion in Romania under Ceausescu

To paraphrase OP's advisor (and Cerberus's comment), sold can indeed be seen as less "accusatory", in that it places more emphasis on the things sold, rather than on the people selling them. This is a very fine nuance, but one which a competent, careful native speaker might well make.