I presume this is a secured network, which is how they require you to agree to the license, but that is an important assumption, so if that's not true, wait a minute.
If the terms that you agreed to state that they will install certain software, they can do that. Consent means consent, i.e. you can freely agree and enjoy certain rights, or refuse and not get those rights. That is where your control comes in. It doesn't matter that it would be "problematic" to not use their service. You have to decide whether you want to use the network, i.e. whether or not the click the "I agree" box. After that point, you have consented.
It's possible that this is an open network, and they have a crazy idea that by accessing that network, you have implicitly agreed to terms that you have not been informed of. Another possibility is that the network is secured but they failed to include a click link prior to logging on, where they would get consent from the user. In that case, you would not have consented to their terms and would not have given them permission to install software on your computers. You have to actually be presented with the agreement and actually agree to the terms. If they did not obtain your consent,
they may have violated the federal Computer Fraud and Abuse Act and state analogs, in installing that software.
Back to the premise that you actually clicked "accept" to access the network.
You don't say what the total set of terms in their agreement is, but if it only says "you agree to let us install this spyware", it's enforceable in that because of that agreement, you can't claim in court that you didn't give them permission to access your computer (which is necessary if you plan to go after them in an illegal access lawsuit).
Consent can be revoked, but there could be technical problems. What you presumably want to be able to do is remove the spyware once you've decided to not use their system. After you uninstall the spyware, their system will presumably prevent you from accessing the system.
There is something unclear in the part where you say "We have been presented with a proposed license agreement that claims that connecting to our organization's WiFi network constitutes consent for them to perform surveillance and install spyware on our personal devices". They can't e.g. email a proposed license to a group leader and think that that constitutes "having obtained consent" from all of the relevant users. I assume this is information and negotiating, and that actual consent will be obtained when a user accesses the network.