Suppose, for a minute, that you understand a prophet to be a man who has divine authority to both speak to God and officially bring his messages to you.
Suppose that you acknowledge and accept that a certain man is, in fact, a real true prophet.
Suppose, then, that he comes to you and says that your deeply held beliefs are at odds with what God wants.
What do you do?
As I see it, you have very few choices.
You can reexamine your beliefs and pray to God to bring your ideas in line with His, being patient and studying from His word (not commentaries on it), and sometimes choosing to not understand. This takes a great deal of humility because it requires that you trust God even if you don't understand what He is doing. It's the ultimate, "Perhaps I am wrong?"
Or you can say, "That man is actually not a prophet. I reject his words. He doesn't talk to God."
Or you can say, in outright rebellion, "God doesn't know what he is doing. I know more than God. I won't change."
Any other response is either disingenuous, or an outright lie, or one of these three in disguise.
With President Packer's death, I've read a few articles about him (very few). He has been an enemy to the liberals for some time, and some of them are writing articles eulogizing him (and, I'm guessing, some are writing celebrating his death, which is kind of appalling).
At least one of the articles captured exactly the liberal mormon attitude I've seen about Elder Packer over the years. It's a startling and scary attitude, where the writers say they acknowledge that he was a prophet, but then say his words deeply offended them, and how hard that must be for HIM, and how holily out-of-touch he was (not hard for them--no hint of accepting that maybe their own personal beliefs are wrong; only that his words were wrong). (You can read it here: http://bycommonconsent.com/2011/10/04/boyd-k-packer-and-prophetic-despair/#more-29663: It's easy to get caught up in the emotional ideas that prophets are lonely and out of sync with the world, and easy to miss the "he was an idiot, too" attitude underlying some of this.) Like I said, I didn't read a lot of articles because I've seen this so many times from liberal friends about Elder Packer that I couldn't stomach any more of it. Either he's a prophet and you're wrong, or he's not a prophet and you might still be wrong, but you might not.
But it's not possible for him to be a prophet and for these liberal friends to also be 100% right like they think they are.
So here's the thing I'm thinking: It's one of three responses if a prophet tells you you're wrong. And then you have three choices of response: you can repent, rebel, or ignore. Two of those don't seem like very smart choices to me, given the "all is well in zion" warnings and the "wicked taketh the truth to be hard" warnings in the scriptures.
But if a prophet says you're wrong, you might be wise to make sure he's really a prophet, and then listen. Because God really does know more than we do, even if He makes no sense to us at all (and especially when He makes little sense, but we make a lot of sense to ourselves. It's so tempting to set our own ideas up as our idols that we worship.)