'Men will treat you the way you let them. There is no such thing as "deserving" respect; you get what you demand from people. Let a guy fuck you in the ass, cum on your back, drink all your beer and then leave, and he'll do it. But if you demand respect, he will either respect you or he won't associate with you.'
This same advice can be adapted for a man who is dealing with a woman (minus the cumming on the back part), as well as homosexual relationships. I see a lot of clients who become punching bags for the people they want to be close with, and many report the same difficulty: "I know I shouldn't let him/her do that, but I just can't stand up for myself." In other words, they intuitively recognize that Tucker's words ring true, but don't know how to put those words into practice. One helpful technique is to step back and think about why are these true statements, from a scientific standpoint.
Humans, by nature, have a work ethic. The "Law of Effect," developed by Edward Thorndike in the early 1900's, tells us that we tend to repeat behaviors that lead to satisfying outcomes. In other words, we do what feels good and leads us toward our goals.
In the short term, many of us tend to approach what is easy, and will repeat behaviors that lead to feeling good. A woman who serves as a doormat takes very little work to maintain (e.g., you don't have to be nice or respectful) and provides short-term satisfaction (free beer, anal sex, and an easily accessible sperm target). In the long-run, however, this tends to bore many of us. In the same vein, a woman may be initially attracted to a man who caters to her every whim and rarely stands up for himself, but ultimately she protests: "I want a man with a spine, someone I can't walk all over!"
Conversely, some people will sacrifice what feels good in the short-term for a potential greater goal in the more distant future. As an example, many people exercise not because they enjoy the workout itself, but because of both the health and cosmetic benefits of exercise in the near and distant future. In interpersonal relationships, the classic example, yet faulty thought process is "If I do what he/she wants, he/she is bound to respect and love me down the line."
Tucker's advice is clear: assert yourself and your needs. However, he also points out that this assertion is not risk-free: a man or woman may, in fact, walk away, seeking an easier short-term goal. Very often, however, this is the exact point where our work ethic kicks in: we ultimately want a challenge, we want someone who doesn't put up with the garbage we dish out, and by asserting yourself, you become that challenge.
What level of challenge do we ultimately seek? Studies done in the workplace suggest that humans thrive most by working toward "moderately difficult" goals. Consider how this might apply in interpersonal relationships: how often do we ultimately walk away from someone who doesn't challenge us in any way? Unless we're particularly lazy, a lot. At the same time, how often do we ultimately give up on the untamable "Bad Boy," or the gorgeous and sophisticated woman who is "out of our league?" Often. People tend to seek out and stay with partners who are fair, yet firm, and push us to be better. This person could be considered a moderate challenge.
The lesson here is that if you are having trouble following Tucker's advice, take a step back and think about our inner work ethic. This awareness and understanding of human behavior (both your own and the other person) can help you to make more informed choices about what is in your best interest. Ultimately, this will help not only protect your beer, back, and every orifice in your body, but will likely lead to more satisfying relationships.