Lying online to hook up, whos guilty?

Now we all know about predators who lie pretending to be young to lure, stalk, and kidnap children but there are in fact other problems that have been created since the popularity of the internet.

There are people who lie about Gender in order to flirt with a particular gender.

1.Girls pretending to be dudes to hook up with various chicks
(Which is a power trip, I dont know why they think this is fun)
2.Girls pretending to be gay guys to get stuff like dick picks from gay men
(This is really messed up) I had friends in HS who did this
3.Guys pretending to be Girls to get stuff from Lesbians

For this I going to discount people who lie for safety concerns. Like lying about gender so you dont get pervs messaging you, or lying about age since you believe you are a bigger target if you put 14 and people who just feel like the other gender. Since generally these are not used with the intent of willfully screwing someone else over.

Along with this we have the reverse age thing where younger people will lie about age in order to flirt with older members since "Age is just a number" saying. Which will often try to convince these older adults to hook up with them and commit to dating them. Which of course is illegal and why I often on websites tend to play unofficial moderator and will often out or report people for flirting with someone outside of a particular age group, since this crap gets people in trouble.

Now depending on what lies about to get with other people can either destroy them emotionally or get them in some major trouble. However you dont know what is real since the other person decided to lie about who they are in an attempt to willfully screw you over. In such a case should the guilt fall on the person who lies or the person who goes along with them not realizing they lied?

Should people just assume everyone online is probobly a liar?