Some poems ought to be rugged, just as some poems ought to be smooth.

When we see a drift of stormy and fantastic clouds at sunset, we do not say that the cloud is beautiful although it is ragged at the edges.

When we see a gnarled and sprawling oak, we do not say that it is fine although it is twisted.

When we see a mountain, we do not say that it is impressive although it is rugged, nor do we say apologetically that it never meant to be rugged, but became so in its striving after strength.

Now, to say that Browning's poems, artistically considered, are fine although they are rugged, is quite as absurd as to say that a rock, artistically considered, is fine although it is rugged.
Ruggedness being an essential quality in the universe, there is that in man which responds to it as to the striking of any other chord of the eternal harmonies.