Protection is the oldest form of sexism. Relate this to Ophelia. Protection is the oldest form of sexism. Relate this to Ophelia.
If you look at what both Laertes and Polonius have to say to Ophelia about her relationship with Hamlet you see what your post suggests as elements of sexism as a form of protection for Ophelia. Laertes speaks to Ophelia just before he leaves for France, and while he is open minded to Ophelia's belief that Hamlet loves her, he strongly cautions her about losing her heart and her honor to Hamlet. He brings to light the very valid point that Hamlet, as a prince, is not going to be able to just marry whomever he wants. Princes are bound to their country's duties, and generally, they marry for political gain, not for true love. Laertes has a rather sexist attitude about both Opehlia's and Hamlet's feelings. He assumes that Hamlet won't remain true to his feelings over his obligations, and that Ophelia isn't being smart enough to protect her heart against the lure that is Hamlet.
Polonius is even more sexist in his attitudes about Hamlet. He dismisses any claim that Hamlet truly loves Ophelia. He tells her that she is a childish fool to believe his "brokers" as true -- he is only saying what he needs to in order to have his way with Ophelia. He speaks of the traditional double standard in regards to the behavior of men vs. women when he says that Hamlet is able to walk on a longer "tether than may be given you [Ophelia]. Hamlet can have his dalliances with no effect to his reputation. Ophelia on the other hand will tarnish the family name and "render me (Polonius) a fool" if she doesn't end this relationship with Hamlet immediately. Polonius doesn't appear to have much confidence in the motives of men, or at least of Hamlet in this case. He is also very insulting and demeaning of Ophelia's feelings and her interpretation of Hamlet's actions. He makes fun of her for taking Hamlet's words for "true pay." His sexism is apparent, but he thinks that he is saying what needs to be said in order to protect Ophelia from ruining her life with a relationship with Hamlet.
While Laertes is not as harsh as Polonius in what he says or how he says it, it is apparent in both conversations that their sexist attitudes are ultimately meant to protect Ophelia's heart and reputation.
I think you can add Hamlet to this list of "protectors" as well. In Act III, directly after his "To be or not to be" soliloquy, Hamlet meets with Ophelia and says the following:
Get thee to a nunnery: why wouldst thou be a
breeder of sinners? I am myself indifferent honest;
but yet I could accuse me of such things that it
were better my mother had not borne me: I am very
proud, revengeful, ambitious, with more offences at
my beck than I have thoughts to put them in,
imagination to give them shape, or time to act them
in. What should such fellows as I do crawling
between earth and heaven? We are arrant knaves,
all; believe none of us. Go thy ways to a nunnery.
If you look at this from a protective standpoint, you can see elements of what both Polonius and Laertes were saying to her. He's telling her not to bother with him, as he is dangerous, "proud, revengeful, ambitious, with more offences at
[his] beck than he [has] thoughts to put them in,/ imagination to give them shape, or time to act them/ in." Under this lens, Hamlet is trying to protect her by telling her to go to a nunnery.
All of these points are true. The men in Ophelia's life are determined ostensibly to protect her but end up controlling her. The result, of course, is her death, and all three of these men share some blame for that. In fairness, though, I also believe protection is one of the oldest and most consistent demonstrations of love. People do fight to protect what they own, but they also fight to protect what they love. The three men in Ophelia's life did, it seems to me, also love her.