To remove the styling, simply remove the link tags that connect the security assist css files.
For example, in my login form, i used the Refined / Pacifica scheam, and set the font formatting to Arial. The css for my login form is:
<link href="WA_SecurityAssist/styles/Refined_Pacifica.css" rel="stylesheet" type="text/css" />
<link href="WA_SecurityAssist/styles/Arial.css" rel="stylesheet" type="text/css" />
If I remove those link tags, I will loose all styling.