I'm trying to modify a web site's Terms of Service, and it feels Great!

Several times, I have given up on joining a web community because I could not accept their terms of service. The problem is a common phrase that makes me too liable (see below). Today I just really wanted to join a website, to participate in their forums. I did join, but I tried something new: I emailed them that I had agreed to modified terms of service, and gave them a month to get back to me if they disagree. I have no idea what legal force this has. MFWAL (My father was a lawyer.)

Here's the obnoxious term. It's a common one on the internet:

"You must be a registered User to create Networks on the [xxx] Platform. Networks and their Network Creators, in turn, determine whether Users need to be registered with [xxx] to contribute Content in that Network. That is up to the discretion of the Network Creator. As a User, you are responsible for keeping your password secure. Names of Social Networks and [xxx] IDs are non-transferable. You will be solely responsible and liable for any activity that occurs under your Ning ID."

The last sentence is the problem. The above paragraph proposes to hold me responsible for anything that might happen if a hacker, or anyone with inside access, figures out how to log in as me, even if I keep my password secret and do not authorize, aid or abet them. I cannot accept responsibility for such events that are totally beyond my control. (In fact, I know of websites that do not even encrypt their user's passwords. This particular website has not told me what they do with my password. They never do!)

I added the following sentence to the above paragraph:

"Except that you will not be responsible and liable for any activity that happens under your Ning ID, having kept your password secure, if another person or computer or computer program logs in as you, without your assistance or authorization, and performs any activity."

I have no idea what's going to happen, but I feel unexpectedly great!
First, I got to use their forums, and even if they throw me off in a few weeks for trying to modify their TOS, I haven't been shut out.
Second, I don't feel like someone is walking over me with their TOS. I agreed to MY form of their TOS, and now I believe I'm negotiating with them.

They have till feb 20 to respond to me. I'm sure I'll be eager to fill you in.