If it is accepted that Avodah Zarah has effectively ceased to exist, as suggested elsewhere on this site, why do we need to follow any of the relevant halachah, that applies to social relationships with non-Jews, use of some of their food and drink, visiting their places of worship, etc? Why do we need to defend ourselves against a threat that is no longer there?
(Note: this answer should not be construed as accepting the premise of the question. It is merely explaining why the conclusion would be rejected even if the premise is correct.)
I’m not sure if the laws you want to abolish are referring to Biblical laws or Rabbinic laws, so let’s address both. Regarding Biblical laws, Maimonides in Guide for the Perplexed 3:34 writes:
From this consideration it also follows that the laws cannot, like medicine, vary according to the different conditions of persons and times; whilst the cure of a person depends on his particular constitution at the particular time, the divine guidance contained in the Law must be certain and general, although it may be effective in some cases and ineffective in others. If the Law depended on the varying conditions of man, it would be imperfect in its totality, each precept being left indefinite. For this reason it would not be right to make the fundamental principles of the Law dependent on a certain time or a certain place; on the contrary, the statutes and the judgments must be definite, unconditional and general, in accordance with the divine words: "As for the congregation, one ordinance shall be for you and for the stranger" (Num. xv. 15); they are intended, as has been stated before, for all persons and for all times.
Regarding Rabbinic laws, Maimonides in Hilchot Mamrim 2:2-3 writes:
The following rules apply when a court issued a decree, instituted an edict, or established a custom and this practice spread throughout the Jewish people and another court arose and sought to nullify the original order and eliminate the original edict, decree, or custom. The later court does not have this authority unless it surpasses the original court in wisdom and in its number of adherents. If it surpasses the original court in wisdom, but not in the number of adherents, or in the number of adherents, but not in wisdom, it cannot nullify its statements. Even if the rationale for which the original court instituted the decree or the edict is nullified, the later court does not have the authority to negate their statements unless they are greater.
How is it possible that the later court will surpass the original court in number? For every Supreme Sanhedrin consists of 71 judges. The intent is the number of sages in the generation who consent and accept the matter stated by the Supreme Sanhedrin without opposing it.
When does the above apply? With regard to matters that were not forbidden to create a safeguard for the words of the Torah, but rather resemble other Torah laws. A different principle applies, by contrast, with regard to matters which the court sought necessary to issue a decree and create a prohibition as a safeguard. If the prohibition spread throughout the Jewish people, another Supreme Sanhedrin does not have the authority to uproot the decree and grant license even if it was of greater stature than the original court.
(Touger translation, my emphasis)