I read this question - Contemporary rabbinic views on social pressure to get people to do Mitzvoth - and it seemed to apply to a recent situation.
I was with a group of friends recently on a Sunday evening in a Northeastern city, getting ready to enter a 100+ year old baseball stadium to see a band that some members have been playing together for 50+ years. Since some of us had travelled from different parts of the country and hadn't seen each other for decades, we celebrated for hours before the show, some of us drinking, some of us smoking a substance that had recently been made completely legal to enjoy in that state.
Along come a couple of Chabad folks, who immediately zeroed in on a couple of Jewish members of the group, trying to get them to lay tefillin. This was in the middle of a huge crowd of concertgoers. They ended up concentrating on one of us, who was doing his best to decline for what he thought were valid reasons - he was intoxicated in various directions and explained he would not be able to concentrate with proper kavanah, it was over 90 humid degrees out and he was sweaty and dirty, etc.
Didn't matter to these guys. They just kept hounding him, slipping candles into his pocket(which of course got confiscated during the entry search), and saying it was just fine to lay tefillin(which they couldn't tell us the last time a sofer checked them to see if they were pasul) in the midst of a raging, wasted crowd, while intoxicated and dirty/sweaty. They kept pushing that it didn't matter, it was the mitzvah alone that counted. It wasn't until we physically walked away and through the entry gates, after the music started (coincidentally, a song called "Samson & Delilah"), that he was left alone and the situation ended.
So - my question is - when presented with extremely pushy people, what is the most polite way of declining? The non-Jewish members of the crowd were ready to politely but firmly turn them around and make sure they kept walking away from us, but we did not let that happen. What words work best in a situation like this?