I think "the line" should be to to treat any employee or work colleague as you would if that person were a customer, client or patient of yours. I guess that would include making no uninvited personal remarks about someone's appearance or love life, no touching - other than shaking hands - no wolf whistling or bottom patting, etc. etc. Surely it is perfectly doable to be friendly and pleasant without engaging in any of the above practices.
Fortunately, I did not have to suffer any of this sort of behaviour in the many jobs I did, other than in my first job as a secretary in a psychiatric hospital. One or two of the consultant psychiatrists for whom I worked when their secretaries were ill or on holiday made remarks and jokes which I found very embarrassing. I recall quite clearly a social psychiatric worker returning from her honeymoon and the unit consultant placing a cushion on a chair before she sat down, remarking (accompanied by a smile) along the lines of she must be feeling sore and delicate after her honeymoon. The young woman looked embarrassed but said nothing - I was very shocked and felt extremely uncomfortable.
I would have felt uncomfortable in a work environment where men flirted, made personal remarks, were "touchy feely", etc. I understand that some women would not find this intimidating but we are not all the same and, that being the case, men (and women) should reserve that sort of behaviour for people they are very close to and know well.
I think I'm right in saying that the law would not become involved if someone wolf whistled or made a one-off personal remark (I'm not sure about the remark made to a Gransnetter that she quoted on here (can't remember who) "I have just had sex with you in my head". I would have found that totally out of order and really creepy, and I think some women would feel very intimidated by it.) Such matter should, I think, be dealt with in the workplace and, if necessary, disciplinary action taken.
But uninvited touching, patting a bottom, etc., could, I believe, be prosecutable. Surely it is not beyond a man (or woman) to undertand this and to desist from behaving in such as way.
I believe putting an arm round a person's shoulder or placing a hand on their lower back to usher them along is the sort of body language that psychologists see as power-related, e.g. it would be highly unlikely for a junior employee to put his or her arm round the shoulder of someone senior to them. It would be equally unusual, I think, for a junior employee to tell a very risque joke to a senior manager unless the senior manager had already set the tone.
Whilst some may disapprove and think it risky for people to "hook up" on Tinder and have casual sex, it is their choice and by consent. It is entirely different from uninvited touching or persistent sexual harassment.
Another poster said "We all put up with some kind of inappropriate touching. We learned to avoid the worst people and laugh about it between ourselves. Lots of snowflakes around these days."
My response to that is you may well feel it is a laughing matter to be inappropriately touched but many women do not and why should they "put up" with behaviour which they find distasteful, demeaning and sometimes frightening? I see it as a form of bullying and I don't think that someone who is being bullied should be called a "snowflake".