Hmmm, If I were to play devil's advocate here and reach for my dub hat once again , I would probably answer something like this - off the top of my head.
We must of course examine the context of the scripture and the times in which the Roman congregation lived. The issues of Jewishness and the old Law were still burning topics among the Bros. Some wanted to keep parts of it, others did not.. Verse 1 to 4 say
14 Welcome the [man] having weaknesses in [his] faith, but not to make decisions on inward questionings. 2 One [man] has faith to eat everything, but the [man] who is weak eats vegetables. 3 Let the one eating not look down on the one not eating, and let the one not eating not judge the one eating, for God has welcomed that one. 4 Who are you to judge the house servant of another? To his own master he stands or falls. Indeed, he will be made to stand, for Jehovah can make him stand.
The days in question here were not "pagan" holidays, they were part of the Jewish Law that some were reluctant to give up. Paul evidently said that there was nothing basically wrong in keeping them, although there was no need to. The situation is different today since the holidays have a pagan origin that is displeasing to Jehovah.....
Not bad for a total fabrication and complete B/S.