Off the top of my head, there are four reasons to "eat less meat":

1) Health. Lots of red meat is not healthy and many of the ways we prepare meat increase carcinogenic load.

2) Expense. Beans will always be cheaper than chicken or steak unless there are powerful subsidies at play. And there are powerful subsidies at play in the United States so this is a muddy one.

3) Social concerns. Meat has a higher impact on the environment than vegetables, from a greenspace perspective as well as a greenhouse gas perspective. Additionally, industrial agriculture produces pretty tremendous runoff waste.

4) Ethical concerns. If you're going to eat an animal someone had to kill it. The level of acceptable suffering caused by one's diet is certainly a contentious subject.

These are four complex problems with many different solutions and nobody is going to come to the same conclusions as someone else. Someone may come to completely different answers at different times of the year. All my vegetarian friends gave up on eating vegetarian in Asia because it simply can't be done. Every time a person reads a little more about food, their perspective on the debate shifts. It's very much a moving target.

And that's why my discussions with vegetarians tend to be nuanced and focused on recipes. I eat vegetarian. I eat vegan occasionally. But I also really cherish a good heritage turkey and even if I cut my bacon consumption way down, it's never going away. I'm fully aware of many different aspects of the issues with meat-eating and have come to my own conclusions. I am comfortable with them at the moment and when that changes, I know ways to return to my comfort levels, be that eating less meat, avoiding certain meat products, etc. There are many dimensions to the subject and a wide-ranging solution-space.

"But have you thought about the ethics?"

There will always be a vocal vegan or vegetarian on public forums that will ignore this dimensionality. They will presume that people who eat meat simply haven't considered the ethical impact of their choices, or are naive to the suffering that eating meat causes instead of recognizing that others have, to coin a term for pure shock value, a higher "threshold of evil". Thus, the discussion devolves into the righteous vegan berating everyone else for their moral failings and everyone else telling the vegan to fuck off.

A tiny percentage of vegetarians wish to hit their conversational partners over the head with their moral choices. A less tiny percentage of vegans do but it's still a small number. An intelligent conversationalist quickly realizes that a conversation about whose lunch choices are more on the side of the angels only serves to piss everyone off and enjoys their salad in peace.

So I'm not sure that an ethical discussion is all that useful - it's a tough conversation to have without debating who is more moral and why. The mechanism of exercising those morals falls by the wayside unless everyone is really careful to keep to the high road and I think this particular subject has been dragged through the mud too much at this point.