In a sense, this does both. It protects the minority party's interests because it allows that party to impede legislation.
But I think that you are asking whether this is, on the whole, a good thing or a bad thing.
In its original conception, this was a good thing. Our system of government is based on the idea that it should be hard for the government to get laws passed. We want it to be difficult so the government will be less able to pass ill-considered laws or laws that tyrannize us. This Senate rule is helpful in this regard because it can be used to block bills if a large minority of the Senate thinks they are bad.
In the last decade or so, however, filibusters have come to be overused. They are now used not on issues of great importance but simply to achieve partisan aims. They have come to be used for more of what I would call selfish reasons.
The basic rule is a good one, but it is used too often today instead of being reserved for really important things.