Hope you don't mind but I copied your opened letter and posted it in one of our small Catholic Forums to find out how they would answer you. I like the following:

Dear Brother in Christ,

It is a blessing to know that you and other Catholics, as well as non-Catholics, find comfort and inspiration in our small ministry; that's what makes this worth while.

The one area I'd counsel caution in is that where you comment on Vatican II and on our bishops. Here we must all be careful not to yield to that spirit of protestantism which is so much a part of our society.

We should not, on our reading of the holy encyclicals of past Holy Fathers, assume we are better placed than the current Holy Father to say how they fit with the tradition of the Church. If we find ourselves thinking that an encyclical or pronouncement by the current Pope or his Blessed predecessor are not in tune with Catholic tradition, we should remember they are blessed with the charism of discernment on these matters and we are not. If we ever find ourselves thinking we are more Catholic than the Pope, we need to stop and ask for a spirit of humility and of wisdom, for that cannot be the case - ever.

Equally, if we find ourselves tempted to call any bishop a heretic, we should stop and ask who gave us the power to say such things about one of our fathers in Christ. Of course we can all be exasperated by what we take to be the lenience of some bishops: conservatively inclined folk see terrible liberalism; liberally inclined folk see rock-ribbed conservatism. By all means, if necessary be critical, but try to be so constructively, and remember, always, it is not seemly in a child of Christ to accuse his father in Christ of heresy. It is the Magisterium which pronounces on such matters, not us. Let us be critical, as I say, on those occasions which call for it, but let us never cause scandal or division by our language or actions.

On the question of the Holy Mass, never forget, even for a second, that it is who we encounter at the Eucharistic feast and not the Rite which matters. If the Pope says that a Rite is valid it is - end of. Rome has spoken, the argument is over.

Of all the parts of being a Catholic, the most difficult one in our society is obedience - followed, perhaps, by humility. The SSPX is no doubt full of men of sincere intent, but where they presume to stand in judgement on the Holy Father, their want of humility leads them from the path of obedience. In so far as the SSPX promotes, intentionally or not, divisions in the Body of Christ, it fails to fulfil Christ's command that we should be one and known by our love each for the other.

In the end, if our conscience is properly formed, we should be able, nay eager, to see the wisdom in what the Holy Father says. We should be mindful of the example of perhaps the greatest of nineteenth century religious thinkers, the Blessed John Henry Newman, who used to say, whenever the Vatican did something he thought particularly unfortunate, that in the long run the Holy Spirit would correct any mistakes. He was right, and we would be wise to imitate such great humility in a man who, better than most of us, was equipped to pronounce on these matters. If he submitted that wisdom to the judgement of the Holy Spirit and Mother Church, we would be well-advised to do the same with our small candle.

In the peace and unity of the Lord.