A covenant with the new order would result in the Society being slowly dissolved from the inside, moulding it gradually according to the blueprint of the revolutionaries so that resistance to the revolt will cease. Catholics do not infiltrate organisations, they wage open war. The modernists have not hesitated to commit things such as habitual perjury to get as far as they have gotten. They swore the Oath against Modernism publically, calling God as their witness, while harbouring other intentions in their hearts. This is the kind of thing that such infiltration brings with it, and that is why Catholics cannot employ such tactics in the war against modernism.
And because Catholics cannot employ such intrinsically evil practices to eradicate modernism, an attempt to infiltrate the new order would have the opposite effect of what is intended; the new order would eventually absorb them into it's pestilent abyss, leaving nothing but an empty shell of appearances.
What we must do is wage open war against everything that stands in the way of rebuilding Christendom in the apostate world. Sealing covenants with those who seek to destroy what Catholics seek to build is simply out of the question if real progress is to be made.
Where I live, there stand beautiful old churches in virtually every village, which were built with the contributions and work of our Catholic fathers, and they were built for the Sacrifice of the Mass. They were built so that right believing Catholics could give worship to the Most High in an athmosphere which gave honour to Him, and which helped the faithful to lift up their thoughts to Him. They were built so that Catholics would hear sound doctrine ringing from the pulpits. Now, they have been usurped by men who have no right to possess these churches, because they are using them at the service of a new religion for which they were not made. They have set up their protestant tables in the sanctuaries, and have used them to propagate their filthy teachings and practices in these once Catholic lands. As long as people keep pretending that such have a right to these buildings, how can they expect to bring Christendom back to the apostate nations?
This is just one example of the necessity to stand firm and not to cave in to the pressure of the world.
Prœliare bella Domini! Fight the battles of the Lord!