Groping and touching anyone inappropriately is never ok.
Doing anything inappropriately is by definition unacceptable. However, when it comes to sexual contact, appropriate is somewhat loosely defined. Prior to being told 'No', appropriate is typically judged on a case by case basis and tends to be weighed heavily on the emotional response of the perceived victim.
In the specific instance Trump described, he did not give any reason to believe that his advances went beyond what was appropriate. Later in the tape he described much more inappropriate actions, but those were described as things he could probably get away with, not things he had actually done or had any intention of doing.
Pursuing a romantic relationship with another man's wife (or vice versa) is never ok.
This statement supposes a sanctity of marriage, which is very much an artificial construct our society inherited from religious institutions of questionable ethical background. The fact that cheating is so commonplace and divorce so frequent casts more than a little doubt on the reasoning behind exclusive monogamous relationships.
In any event, stating that pursuit of a romantic relationship with another person's partner is never acceptable completely ignores that possibility of a scenario in which all parties have given consent, which is not entirely uncommon.
Manipulating someone else for the sole purpose of sexual gratification is never ok.
I would argue that there is nothing implicitly wrong with pursuit of sexual gratification; it's a completely natural impulse, and when done safely, is mechanically harmless. Emphasis on mechanically. There are of course emotional concerns, but those are the responsibility of each party to evaluate for themselves before giving consent.
As for manipulation, that is an extremely broad term. Almost everything we do is a manipulation to some degree. Saying that manipulation is wrong is like saying that living in modern society is wrong.