Determinism is that every belief and action you have or do is caused to happen by the physical universe, and I find this thought infuriating to put it lightly. Thinking that everything we will do is already determined, which completely kills the notion of Free Will and making our own choices, is absurd. I have some belief in fate, but never to the extreme that determinism takes it. Determinism, if true, takes away everything from humans, all power, all responsibility, and basically makes us puppets in some play.
With determinism, never will somebody be blamed for their actions, for they were "determined" to do what they did, and "had no choice." On the flip side, somebody's successes can never be attributed to their work either, for they were "determined" to achieve whatever they achieved. Just think if somebody took everything you accomplished, which you take pride in, and basically said you had nothing to do with any of them, that they basically were just handed to you, wouldn't that piss you off? Determinism is just a huge excuse to take all blame off of humankind, which to me is bullshit.
Determinism also interferes with religious beliefs. Some of the common beliefs of God are that of an All-Loving God, and possibly some notion of Heaven and Hell to name a couple. Now if your religious beliefs fall into these categories, determinism, in my opinion tears these down. If there is a Heaven and Hell, and determinism is true, wouldn't that mean that God determined us to go to either one of the other once we die? This defeats the belief of an All-Loving God, because an All-Loving God would not condemn us to Hell since before we were born. So if God is All-Loving and determinism exists, that would mean everybody goes to Heaven (which goes against many beliefs,) there is no Heaven or Hell (which makes everybody's "afterlife" equal,) or the most drastic, there is no God (or at least no All-Loving one.) All of this added up to me makes determinism horrible to even consider, and I refuse to believe in it.