It seems you have opened multiple queries in one thread ! I would like to express my views here.
1. I think they all have developed Ostrich Syndrome :) I hope you have already sent a written warning to them! Now, it is as easy as sending them a pink slip under disciplinary actions.
2. Well, all of you must have attended 'Sexual Harassment Awareness' training at your workplace! If someone is uncomfortable with such jokes then stop circulating those mails immediately.
3. As per Maternity Benefit Act, the woman is entitled to take leave upto 6 months. Did she utilize all of it? Did she already report back to work? I think, she can ask for light work only prior to going on maternity leave.
4. Complicacy is involved! You should have set these rules in the job description or job offer or from day1 etc ...
5. I think, here is a need of more managerial skills required than seeking lawyering skills. You may want to bring this issue to his attention in a more diligent manner! Ultimately, it is employer's responsibility to prevent such discrimination at workplace, otherwise the Company would suffer from all possible ways!
Let us hear from other members too !!