How do I - as a Catholic - view ecumenism?
Firstly, we have to acknowledge that the Catholic Church has joined the ecumenical movement that was originally launched by protestants.
We also know that many Eastern Orthodox brethren condemn ecumenism as a heresy.
My personal take?
Since the Church has accepted it, I do as well. However, I differentiate between a good ecumenism and a bad ecumenism. What do I mean when I use those adjectives? I mean that ecumenism can have both positive and negative fruits: and we as the Church ought to do our best to strive only for the good fruits.
Since I live in Germany, I can say form personal experience what really happens in the ecumenical movement in the lowest part: the parish life. There you would have Catholics and protestants taking the ecumenical talks a bit further forgetting about the boundaries of decency and truth: Catholics participating in protestant "last supper meals" and protestants recieving the Body of Christ from Catholic clerics. Many lay persons even condemn the prohibition of such unlawful practices with the argument "we're all Christians anyways".
It is true that we are all Christians, but we are not all right and there is but one Church: that's the Catholic Church.
So basically, the bad type of ecumenism takes places when the truth becomes blurry, when people try to create a false sense of unity, a superficial one that would break down right away once in-depth-talks take place.
What do I think should be our goal in ecumenism? It is simple: our goal ought to be this:
to lead our brethren in error back to unity with the chair of Peter
Does that mean, I want to convert protestants? Sure: why not? We know there is but one Church and only in this Church cam there be solid hope for salvation as promised by our Lord Jesus Christ.
So from my perspective: we hold the truth, we are not allowed to water it down for the sake of illusory unity and for the sake of being liked by the world.
I will close with the words of St. Cyprian of Carthage:
The Lord says to Peter: I say to you, he says, that you are Peter, and upon this rock I will build my Church. . . . On him [Peter] he builds the Church, and to him he gives the command to feed the sheep [John 21:17], and although he assigns a like power to all the apostles, yet he founded a single chair [cathedra], and he established by his own authority a source and an intrinsic reason for that unity. Indeed, the others were that also which Peter was [i.e., apostles], but a primacy is given to Peter, whereby it is made clear that there is but one Church and one chair. So too, all [the apostles] are shepherds, and the flock is shown to be one, fed by all the apostles in single-minded accord. If someone does not hold fast to this unity of Peter, can he imagine that he still holds the faith? If he [should] desert the chair of Peter upon whom the Church was built, can he still be confident that he is in the Church?" (The Unity of the Catholic Church 4; 1st edition [A.D. 251]).