I am a (female) IT student working in an IT company. So far I enjoy work, I get along well with my colleagues and the office atmosphere is friendly.
Last week although, I overheard a conversation in our shared office between a senior colleague "Bob" who is going to be a manager soon and a younger colleague "Jim". They were talking about a professional conference both had attended and at one point Bob said to Jim: "You know, this girl who gave the machine learning talk, she was hot!", followed by laughter.
For several reasons I don't think this comment was professional nor adequately respectful by Bob and it keeps me worrying that a potentially negative (i.e. sexist) work culture might grow in our office. Those reasons are
Such a behavior can be career damaging: As a junior, giving a professional talk is a chance to prove some solid knowledge in your specific field in front of powerful people. Often, one of the intentions behind giving the talk is to build up a good reputation, being known as a person who could give professional advice, who could be hired or invited for another talk. If the first and most prevalent impression about the presenter is his or her appearance, chances getting lowered he or she might be associated as a potential hiring candidate in the first place (being known as "the machine learning girl" vs "the hot girl"). Sure, no one can just stop noticing someones appearance, but someones attractiveness should not be discussed at work.
Bob is a senior employee, he is soon going to be a manager. He is a role model for younger employees. If he keeps on talking about other professionals like this, juniors might pick up such a behavior. Especially when it's an easy way for common laughter.
Females could feel uncomfortable: (this is somewhat personal) I don't want to work in a company where I have to worry about looking 'distracting', or having colleagues discussing my attractiveness. I am going to give a talk at the company soon as well.
I need to address this issue in order to continue enjoying the work environment and especially to keep a good relationship to Bob. I want to speak to Bob personally, I don't plan to call him out to HR as this is a minor incident and most of all because I want to prove to myself that I can handle conflicts on my own. As far as I got to know Bob, he would at least listen to me.
So here's my question: How do I, a junior, discuss this issue respectfully with Bob, a senior, in a way that he understands the negative impact of his comment without coming off as "annoying" or "troublesome"?
To clarify, I don't think it's worrisome in general if a man calls a woman "hot". I wouldn't mind if Bob had told Jim about this after work in a bar or if Bob would've said this about his partner.
EDIT: The conversation was held in an office which is shared by 8 people (including me). The conversation was loud enough for everyone to hear. The woman they were talking about was not a colleague, but another professional at a conference. My problem is about the setting in which the comment was expressed (at work + about a conference participant). I work in Germany. Bob and Jim knew I heard the comment and they expected me to react as they were looking in my direction saying "Uh she didn't hear?". I suspect they knew their comment was not totally okay. At that time all I could say was "Such comments are annoying.". I don't think both understand why exactly I think this was "annoying" and now I don't think "annoying" is the word that expresses best my criticism about it and I think saying "annoying" might have been slightly rude. That's why I want to clarify it. I didn't mention it in the original post because I thought this was not that relevant, but your questions show that there was need for further information.