Never let the emotion of their inappropriate behaviour cause you to lose your cool.
As doubtfull1799 says, it will only reinforce their idea that WE are the mentally diseased ones....
Remember the scripture that says "return evil for evil to no-one...as far as it depends on you, be peaceable with all"
However, that doesn't mean we cant politely yet firmly remind them of "APPROPRIATE BOUNDARIES" and behaviour!
Many elders feel that they have the power over us and the right to overstep appropriate boundaries.
However the only power they have over us is that which we allow